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Compare  the  unfavorable  artificial  environment  of  a  crowded  city  with  the  more 

favorable  environment  of  the  country. 


A  CIVIC   BIOLOGY 


Presented  in  Problems 


BY 

GEORGE   WILLIAM  HUNTER,   Pii.D. 

HEAD    OF   THE   DEPARTMENT   OF   BIOLOGY,    DE    WITT   CLINTON 

HIGH  SCHOOL,    CITY   OF   NEW   YORK. 

AUTHOR   OF   "elements   OF   BIOLOGY,"    "ESSENTIALS   OF 

BIOLOGY,"   ETC. 


AMERICAN  BOOK  COMPANY 

NEW  YORK  CINCINNATI  CHICAGO 


Copyright,  1914,  by 
GEORGE   WILLIAM   HUNTER. 

Copyright,  1914,  in  Great  Britain. 


HUNTER,    CIVIC    BIOLOGY. 

W.  p.   12 


DeMcateb 

TO    MY 

FELLOW    TEACHERS 

OF    THE    DEPARTMENT    OF    BIOLOGY 

IN    THE    DE    WITT    CLINTON    HIGH    SCHOOL 

WHOSE   CAPABLE,  EARNEST,  UNSELFISH 

AND    INSPIRING    AID    HAS    MADE 

THIS    BOOK    POSSIBLE 


17530 


FOREWORD   TO   TEACHERS 

A  COURSE  in  biology  given  to  beginners  in  the  secondary  school 
should  have  certain  aims.  These  aims  must  be  determined  to  a 
degree,  first,  by  the  capabilities  of  the  pupils,  second,  by  their 
native  interests,  and,  third,  by  the  environment  of  the  pupils. 

The  boy  or  girl  of  average  ability  upon  admission  to  the  second- 
ary school  is  not  a  thinking  individual.  The  training  given  up  to 
this  time,  with  but  rare  exceptions,  has  been  in  the  forming  of 
simple  concepts.  These  concepts  have  been  reached  didactically 
and  empirically.  Drill  and  memory  work  have  been  the  peda- 
gogic vehicles.  Even  the  elementary  science  work  given  has 
resulted  at  the  best  in  an  interpretation  of  some  of  the  common 
factors  in  the  pupil's  environment,  and  a  widening  of  the  mean- 
ing of  some  of  his  concepts.  Therefore,  the  first  science  of  the 
secondary  school,  elementary  biology,  should  be  primarily  the 
vehicle  by  which  the  child  is  taught  to  solve  problems  and  to  think 
straight  in  so  doing.  No  other  subject  is  more  capable  of  logical 
development.  No  subject  is  more  vital  because  of  its  relation 
to  the  vital  things  in  the  life  of  the  child.  A  series  of  experiments 
and  demonstrations,  discussed  and  applied  as  definite  concrete 
problems  which  have  arisen  within  the  child's  horizon,  will  develop 
power  in  thinking  more  surely  than  any  other  subject  in  the  first 
year  of  the  secondary  school. 

But  in  our  eagerness  to  develop  the  power  of  logical  thinking 
we  must  not  lose  sight  of  the  previous  training  of  our  pupil.  Up 
to  this  time  the  method  of  induction,  that  handmaiden  of  logical 
thought,  has  been  almost  unknown.  Concepts  have  been  formed 
deductively  by  a  series  of  comparisons.  All  concepts  have  been 
handed  down  by  the  authority  of  the  teacher  or  the  text;  the 
inductive  search  for  the  unkno^\Ti  is  as  yet  a  closed  book.  It  is 
unwise,  then,  to  directly  introduce  the  pupil  to  the  method  of  in- 
duction with  a  series  of  printed  directions  which,  though  definite 
in  the  naind  of  the  teacher  because  of  his  wider  horizon,  mijan 


HOfERTY  LIBURY 


8  FOREWORD  TO  TEACHERS 

little  or  nothing  as  a  definite  problem  to  the  pupil.  The  child 
must  be  brought  to  the  appreciation  of  the  problem  through  the 
deductive  method,  by  a  comparison  of  the  future  problem  with 
some  definite  concrete  experience  within  his  own  field  of  vision. 
Then  by  the  inductive  experiment,  still  led  by  a  series  of  oral 
questions,  he  comes  to  the  real  end  of  the  experiment,  the  conclu- 
sion, with  the  true  spirit  of  the  investigator.  The  result  is  tested 
in  the  light  of  past  experiment  and  a  generalization  is  formed  which 
means  something  to  the  pupil. 

For  the  above  reason  the  laboratory  problems,  which  naturally 
precede  the  textbook  work,  should  be  separated  from  the  subject 
matter  of  the  text.  A  textbook  in  biology  should  serve  to  verify 
the  student's  observations  made  in  the  laboratory,  it  should  round 
out  his  concept  or  generalization  by  adding  such  material  as  he 
cannot  readily  observe  and  it  should  give  the  student  directly 
such  information  as  he  cannot  be  expected  to  gain  directly  or 
indirectly  through  his  laboratory  experience.  For  these  reasons 
the  .laboratory  manual  has  been  separated  from  the  text. 

"The  laboratory  method  was  such  an  emancipation  from  the  old-time 
bookish  slavery  of  pre-laboratory  days  that  we  may  have  been  inclined 
to  overdo  it  and  to  subject  ourselves  to  a  new  slavery.  It  should  never 
be  forgotten  that  the  laboratory  is  simply  a  means  to  the  end ;  that  the 
dominant  thing  should  be  a  consistent  chain  of  ideas  which  the  laboratory 
may  serve  to  elucidate.  When,  however,  the  laboratory  assumes  the  first 
place  and  other  phases  of  the  course  are  made  explanatory  to  it,  we  have 
taken,  in  my  mind,  an  attitude  fundamentally  wrong.  The  question  is, 
not  what  types  may  be  taken  up  in  the  laboratory  to  be  fitted  into  the 
general  scheme  afterwards,  but  what  ideas  are  most  worth  while  to  be 
worked  out  and  developed  in  the  laboratory,  if  that  happens  to  be  the 
best  way  of  doing  it,  or  if  not,  some  other  way  to  be  adopted  with  perfect 
freedom.  Too  often  our  course  of  study  of  an  animal  or  plant  takes  the 
easiest  rather  than  the  most  illuminating  path.  What  is  easier,  for  in- 
stance, particularly  with  large  classes  of  restless  pupils  who  apparently 
need-to  be  kept  in  a  condition  of  uniform  occupation,  than  to  kill  a  supply 
of  animals,  preferably  as  near  alike  as  possible,  and  set  the  pupils  to  work 
drawing  the  dead  remains?  This  method  is  usually  supplemented  by  a 
series  of  questions  concerning  the  remains  which  are  sure  to  keep  the 
pupils  busy  a  while  longer,  perhaps  until  the  bell  strikes,  and  which  usu- 
ally are  so  planned  as  to  anticipate  any  ideas  that  might  naturally  crop 
up  in  the  pupil's  mind  during  the  drawing  exercise. 


FOREWORD   TO  TEACHERS  9 

"  Such  an  abuse  of  the  laboratory  idea  is  all  wrong  and  should  be  avoided. 
The  ideal  laboratory  ought  to  be  a  retreat  for  rainy  days ;  a  substitute 
for  out  of  doors ;  a  clearing  house  of  ideas  brought  in  from  the  outside. 
Any  course  in  biology  which  can  be  confined  within  four  walls,  even  if 
these  walls  be  of  a  modern,  well-equipped  laboratory,  is  in  some  measure 
a  failure.  Living  things,  to  be  appreciated  and  correctly  interpreted, 
must  be  seen  and  studied  in  the  open  where  they  will  be  encountered 
throughout  Hfe.  The  place  where  an  animal  or  plant  is  found  is  just  as 
important  a  characteristic  as  its  shape  or  function.  Impossible  field  excur- 
sions with  large  classes  within  school  hours,  which  only  bring  confusion  to 
inflexible  school  programs,  are  not  necessary  to  accomphsh  this  result. 
Properly  administered,  it  is  without  doubt  one  of  our  most  efficient  de- 
vices for  developing  biological  ideas,  but  the  laboratory  should  be  kept  in 
its  proper  relation  to  the  other  means  at  our  disposal  and  never  be  allowed 
to  degenerate  either  into  a  place  for  vacuous  drawing  exercises  or  a  bio- 
logical morgue  where  dead  remains  are  viewed."  —  Dr.  H.  E.  Walter. 

For  the  sake  of  the  pupil  the  number  of  technical  and  scientific 
terms  has  been  reduced  to  a  minimum.  The  language  has  been 
made  as  simple  as  possible  and  the  problems  made  to  hinge  upon 
material  already  known,  by  hearsay  at  least,  to  the  pupil.  So  far 
as  consistent  with  a  well-rounded  course  in  the  essentials  of  bio- 
logical science,  the  interests  of  the  children  have  been  kept  in  the 
foreground.  In  a  recent  questionnaire  sent  out  by  the  author  and 
answered  by  over  three  thousand  children  studying  biology  in  the 
secondary  schools  of  Connecticut,  Massachusetts,  New  Jersey, 
and  New  York  by  far  the  greatest  number  gave  as  the  most 
interesting  topics  those  relating  to  the  care  and  functions  of  the 
human  body  and  the  control  and  betterment  of  the  environment. 
As  would  be  expected,  boys  have  different  biological  interests  from 
girls,  and  children  in  rural  schools  wish  to  study  different  topics 
from  those  in  congested  districts  in  large  communities.  The  time 
has  come  when  we  must  frankly  recognize  these  interests  and 
adapt  the  content  of  our  courses  in  biology  to  interpret  the 
immediate  world  of  the  pupil. 

With  this  end  in  view  the  following  pages  have  been  Awitten. 
This  book  shows  boys  and  girls  living  in  an  urban  community 
how  they  may  best  live  within  their  own  environment  and  how 
they  may  cooperate  with  the  civic  authorities  for  the  betterment 
of  their  environment.     A  logical  course  is  built  up  around  the 


10  FOREWORD  TO   TEACHERS 

topics  which  appeal  to  the  average  normal  boy  or  girl,  topics  given 
in  a  logical  sequence  so  as  to  work  out  the  solution  of  problems 
bearing  on  the  ultimate  problem  of  the  entire  course,  that  of  prep- 
aration for  citizenship  in  the  largest  sense. 

Seasonal  use  of  materials  has  been  kept  in  mind  in  outlining 
this  course.  Field  trips,  when  properly  organized  and  later  used 
as  a  basis  for  discussion  in  the  classroom,  make  a  firm  foundation 
on  which  to  build  the  superstructure  of  a  course  in  biology.  The 
normal  environment,  its  relation  to  the  artificial  environment  of 
the  city,  the  relations  of  mutual  give  and  take  existing  between 
plants  and  animals,  are  better  shown  by  means  of  field  trips  than 
in  any  other  way.  Field  and  museum  trips  are  enjoyed  by  the 
pupils  as  well.  These  result  in  interest  and  in  better  work.  The 
course  is  worked  up  around  certain  great  biological  principles ; 
hence  insects  may  be  studied  when  abundant  in  the  fall  in  connec- 
tion with  their  relations  to  green  plants  and  especially  in  their  re- 
lation to  flowers.  In  the  winter  months  material  available  for  the 
laboratory  is  used.  Saprophytic  and  parasitic  organisms,  wild 
plants  in  the  household,  are  studied  in  their  relations  to  man- 
kind, both  as  destroyers  of  food,  property  and  life  and  as  man's 
invaluable  friends.  The  economic  phase  of  biology  may  well  be 
taken  up  during  the  winter  months,  thus  gaining  variety  in  sub- 
ject matter  and  in  method  of  treatment.  The  apparent  emphasis 
placed  upon  economic  material  in  the  following  pages  is  not  real. 
It  has  been  found  that  material  so  given  makes  for  variety,  as  it 
may  be  assigned  as  a  topical  reading  lesson  or  simply  used  as 
reference  when  needed.  Cyclic  work  in  the  study  of  life  phenom- 
ena and  of  the  needs  of  organisms  for  oxygen,  food,  and  reproduc- 
tion culminates,  as  it  rightly  should,  in  the  study  of  life-processes 
of  man  and  man's  relation  to  his  environment. 

In  a  course  in  biology  the  difficulty  comes  not  so  much  in  know- 
ing what  to  teach  as  in  knowing  what  not  to  teach.  The  author 
believes  that  he  has  made  a  selection  of  the  topics  most  vital  in  a 
well-rounded  course  in  elementary  biology  directed  toward  civic 
betterment.  The  physiological  functions  of  plants  and  animals, 
the  hygiene  of  the  individual  within  the  community,  conservation 
and  the  betterment  of  existing  plant  and  animal  products,  the 


FOREWORD  TO   TEACHERS  11 

big  underlying  biological  concepts  on  which  society  is  built,  have 
all  been  used  to  the  end  that  the  pupil  will  become  a  better, 
stronger  and  more  unselfish  citizen.  The  ''  spiral  "  or  cyclic 
method  of  treatment  has  been  used  throughout,  the  purpose  being 
to  ultimately  build  up  a  number  of  well-rounded  concepts  by 
constant  repetition  but  with  constantly  varied  viewpoint. 

The  sincere  thanks  of  the  author  is  extended  to  all  who  have 
helped  make  this  book  possible,  and  especially  to  the  members 
of  the  Department  of  Biology  in  the  De  Witt  Clinton  High  School. 
Most  of  the  men  there  have  directly  or  indirectly  contributed 
their  time  and  ideas  to  help  make  this  book  worth  more  to  teachers 
and  pupils.  The  following  have  read  the  manuscript  in  its  entirety 
and  have  offered  much  valuable  constructive  criticism  :  Dr.  Herbert 
E.  Walter,  Professor  of  Zoology  in  Brown  University ;  Miss  Elsie 
Kupfer,  Head  of  the  Department  of  Biology  in  Wadleigh  High 
School;  George  C.  Wood,  of  the  Department  of  Biology  in  the 
Boys'  High  School,  Brooklyn  ;  Edgar  A.  Bedford,  Head  of  Depart- 
ment of  Biology  in  the  Stuyvesant  High  School ;  George  E.  Hew- 
itt, George  T.  Hastings,  John  D.  McCarthy,  and  Frank  M.  Wheat, 
all  of  the  Department  of  Biology  in  the  De  Witt  Clinton  High 
School. 

Thanks  are  due,  also,  to  Professor  E.  B.  Wilson,  Professor  G.N. 
Calkins,  Mr.  WllHam  C.  Barbour,  Dr.  John  A.  Sampson,  W.  C. 
Stevens,  and  C.  W.  Beebe,  Dr.  Alvin  Davison,  and  Dr.  Frank 
Overton;  to  the  United  States  Department  of  Agriculture;  the 
New  York  Aquarium  ;  the  Charity  Organization  Society ;  and  the 
American  Museum  of  Natural  History,  for  permission  to  copy  and 
use  certain  photographs  and  cuts  which  have  been  found  useful  in 
teaching.  Dr.  Charles  H.  Morse  and  Dr.  Lucius  J.  Mason,  of  the 
De  Witt  Clinton  High  School,  prepared  the  hygiene  outline  in  the 
appendix.  Frank  M.  Wheat  and  my  former  pupil,  John  W.  Teitz, 
now  a  teacher  in  the  school,  m.ade  many  of  the  fine  dra^vings  and 
took  several  of  the  photographs  of  experiments  prepared  for  this 
book.     To  them  especially  I  wish  to  express  my  thanks. 

At  the  end  of  each  of  the  following  chapters  is  a  list  of  books 
which  have  proved  their  use  either  as  reference  reading  for  students 
or  as  aids  to  the  teacher.     Most  of  the  books  mentioned  are  within 


12  FOREWORD  TO  TEACHERS 

the  means  of  the  small  school.  Two  sets  are  expensive  :  one,  The 
Natural  History  of  Plants,  by  Kerner,  translated  by  Oliver,  pub- 
lished by  Henry  Holt  and  Company,  in  two  volumes,  at  $11 ;  the 
other.  Plant  Geography  upon  a  Physiological  Basis,  by  Schimper, 
pubHshed  by  the  Clarendon  Press,  $12 ;  but  both  works  are  inval- 
uable for  reference. 

For  a  general  introduction  to  physiological  biology,  Parker, 
Elementary  Biology,  The  Macmillan  Company ;  Sedgwick  and 
Wilson,  General  Biology,  Henry  Holt  and  Company;  Verworn, 
General  Physiology,  The  Macmillan  Company ;  and  Needham,  Gen- 
eral Biology,  Comstock  Publishing  Company,  are  most  useful  and 
inspiring  books. 

Two  books  stand  out  from  the  pedagogical  standpoint  as  by  far 
the  most  helpful  of  their  kind  on  the  market.  No  teacher  of 
botany  or  zoology  can  afford  to  be  without  them.  They  are : 
Lloyd  and  Bigelow,  The  Teaching  of  Biology,  Longmans,  Green, 
and  Company,  and  C.  F.  Hodge,  Nature  Study  and  Life,  Ginn  and 
Company.  Other  books  of  value  from  the  teacher's  standpoint 
are :  Ganong,  The  Teaching  Botanist,  The  Macmillan  Company ; 
L.  H.  Bailey,  The  Nature  Study  Idea,  Doubleday,  Page,  and  Com- 
pany ;  and  McMurry's  How  to  Study,  Houghton  Mifflin  Company. 


CONTENTS 


CHAPTER  PAGB 

Foreword  to  Teachers 7 


15 

19 

'28 
47 


I.     Some  Reasons  for  the  Study  of  Biology 
II.     The  Environment  of  Plants  and  Animals    . 

III.  The  Interrelations  of  Plants  and  Animals 

IV.  The  Functions  and  Composition  of  Living  Things 
V.     Plant  Growth  and  Nutrition  —  The  Causes  of  Growth      58 

VI.     The  Organs  of  Nutrition  in  Plants  —  The  Soil  and 

ITS  Relation  to  Roots 71 

VII.     Plant  Growth  and  Nutrition — Plants  make  Food  .      84 
VIII.     Plant  Growth  and  Nutrition  —  The  Circulation  and 

Final  Uses  of  Food  by  Plants  ....      97 

IX.     Our  Forests,  their  Uses  and  the  Necessity  of  their 

Protection 105 

X.     The  Economic  Relation  of  Green  Plants  to  Man     .     117 
XI.     Plants  without   Chlorophyll  in  their   Relation   to 

Man 180 

XII.     The  Relations  of  Plants  to  Animals    ....     159 

XIII.  Single-celled  Animals  considered  as  Organisms        .     166 

XIV.  Division  of  Labor,  the  Various  Forms  of  Plants  and 

Animals 173 

XV.     The  Economic  Importance  of  Animals   ....     197 

XVI.     An  Introductory  Study  of  Vertebrates      .        .        .    232 

XVII.     Heredity,  Variation,  Plant  and  Animal  Breeding    .     249 

XVIII.     The  Human  Machine  and  its  Needs       ....    2(56 

XIX.     Foods  and  Dietaries 272 

XX.    Digestion  and  Absorption 296 

18 


14  CONTENTS 

CHAPTEB  PA3E 

XXL    The  Blood  and  its  Circulation 313 

XXII.     Respiration  and  Excretion 329 

XXIII.  Body  Control  and  Habit  Formation      ....  348 

XXIV.  Man's  Improvement  of  his  Environment        .        .        .  373 
XXV.    Some  Great  Names  in  Biology 398 

APPENDIX 407 

Suggested  Course  with  Time  Allotment  and  Sequence 

OP  Topics  for  Course  beginning  in  Fall        .        .  407 
Suggested  Syllabus  for  Course  in  Biology  beginning 

in  February  and  ending  the  Next  January        .  411 

Hygiene  Outline 415 

Weights,  Measures,  and  Tempp:ratures          .        .        .  417 

Suggestions  for  Laboratory  Equipment       .        .        .  418 

INDEX c  419 


A  CIVIC  BIOLOGY 


I.   THE   GENERAL   PROBLEM— SOME   REASONS   FOR 

THE   STUDY  OF   BIOLOGY 

What  is  Biology  ?  —  Biology  is  the  study  of  living  beings,  both 
plant  and  animal.^  Inasmuch  as  man  is  an  animal,  the  study  of 
biology  includes  the  study  of  man  in  his  relations  to  the  plants 
and  the  animals  which  surround  him.  Most  important  of  all 
is  that  branch  of  biology  which  treats  of  the  mechanism  we  call 
the  human  body,  —  of  its  parts  and  their  uses,  and  its  repair. 
This  subject  we  call  human  physiology. 

Why  study  Biology?  —  Although  biology  is  a  very  modern 
science,  it  has  found  its  way  into  most  high  schools;  and  an  in- 
creasingly large  number  of  girls  and  boys  are  yearly  engaged  in  its 
study.  These  questions  might  well  be  asked  by  any  of  the  students  : 
Why  do  I  take  up  the  study  of  biology  ?  Of  what  practical  value 
is  it  to  me  ?  Besides  the  discipline  it  gives  me,  is  there  anything 
that  I  can  take  away  which  will  help  me  in  my  future  life  ? 

Human  Physiology.  —  The  answer  to  this  question  is  plain. 
If  the  study  of  biology  will  give  us  a  better  understanding  of  our 
own  bodies  and  their  care,  then  it  certainly  is  of  use  to  us.  That 
phase  of  biology  known  as  physiology  deals  with  the  uses  of  the 
parts  of  a  plant  or  animal ;  human  physiology  and  hygiene  deal 
with  the  uses  and  care  of  the  parts  of  the  human  animal.  The 
prevention  of  sickness  is  due  in  a  large  part  to  the  study  of  hygiene. 
It  is  estimated  that  over  twenty-five  per  cent  of  the  deaths  that 
occur  yearly  in  this  country  could  be  averted  if  all  people  lived  in 
a  hygienic  manner.  In  its  application  to  the  lives  of  each  of  us,  as 
a  member  of  our  family,  as  a  member  of  the  school  we  attend, 
and  as  a  future  citizen,  a  knowledge  of  hygiene  is  of  the  greatest 
importance. 

Relations  of  Plants  to  Animals.  —  But  there  are  other  reasons 
why  an  educated  person  should  know  something  about  biology. 

15 


16        SOME  REASONS   FOR   STUDYING   BIOLOGY 

We  do  not  always  realize  that  if  it  were  not  for  the  green  plants, 
there  would  be  no  animals  on  the  earth.  Green  plants  furnish 
food  to  animals.  Even  the  meat-eating  animals  feed  upon  those 
that  feed  upon  plants.  How  the  plants  manufacture  this  food 
and  the  relation  they  bear  to  animals  will  be  discussed  in  later 
chapters.  Phmts  furnish  man  with  the  greater  part  of  his  food 
in  the  form  of  grains  and  cereals,  fruits  and  nuts,  edible  roots  and 
h'aves ;  they  provide  his  domesticated  animals  with  food ;  they 
giv(»  him  timber  for  his  houses  and  wood  and  coal  for  his  fires ; 
they  provide  him  with  pulp  wood,  from  which  he  makes  his  paper, 
and  oak  galls,  from  which  he  may  make  ink.  Much  of  man's  cloth- 
ing and  the  thread  with  which  it  is  sewed  together  come  from 
fiber-producing  plants.  Most  medicines,  beverages,  flavoring  ex- 
tracts, and  spices  are  plant  products,  while  plants  are  made  use  of 
in  hundreds  of  ways  in  the  useful  arts  and  trades,  producing  var- 
nishes, dyestuffs,  rubber,  and  other  products. 

Bacteria  in  their  Relation  to  Man.  —  In  still  another  way,  cer- 
tain i^lants  vitall}^  affect  mankind.  Tiny  plants,  called  bacteria, 
so  small  that  millions  can  exist  in  a  single  drop  of  fluid,  exist 
almost  everywhere  about  us,  —  in  water,  soil,  food,  and  the  air. 
They  play  a  tremendous  part  in  shaping  the  destiny  of  man  on 
the  earth.  They  help  him  in  that  they  act  as  scavengers,  causing 
things  to  decay ;  thus  they  remove  the  dead  bodies  of  plants  and 
animals  from  the  surface  of  the  earth,  and  turn  this  material  back 
to  the  ground  ;  they  assist  the  tanner ;  they  help  make  cheese  and 
])utter ;  they  improve  the  soil  for  crop  growing ;  so  the  farmer  can- 
not do  without  them.  But  they  likewise  sometimes  spoil  our  meat 
and  fish,  and  our  vegetables  and  fruits;  they  sour  our  milk,  and 
may  make  our  canned  goods  spoil.  Worst  of  all,  they  cause  dis- 
eases, among  others  tuberculosis,  a  disease  so  harmful  as  to  be 
called  the  "  white  plague."  Fully  one  half  of  all  yearly  deaths  are 
caused  by  these  plants.  So  important  are  the  bacteria  that  a  sub' 
division  of  biology,  called  bacteriology,  has  been  named  after  them, 
and  hundreds  of  scientists  are  devoting  their  lives  to  the  study  of 
bacteria  and  their  control.  The  greatest  of  all  bacteriologists, 
Louis  Pasteur,  once  said,  ''  It  is  within  the  power  of  man  to  cause 
all  parasitic  diseases  (diseases  mostly  caused  by  bacteria)  to  disap- 


SOME  REASONS  FOR  STUDYING  BIOLOGY        17 

pear  from  the  world."  His  prophecy  is  gradually  being  fulfilled, 
and  it  may  be  the  lot  of  some  boys  or  girls  who  read  this  book  to 
do  their  share  in  helping  to  bring  this  condition  of  affairs  about. 

The  Relation  of  Animals  to  Man.  —  Animals  also  play  an  im- 
portant part  in  the  world  in  causing  and  carrying  disease.  Ani- 
mals that  cause  disease  are  usually  tiny,  and  live  in  other 
animals  as  parasites  ;  that  is,  they  get  their  living  from  their  hosts 
on  which  they  feed.  Among  the  diseases  caused  by  parasitic 
animals  are  malaria,  yellow  fever,  the  sleeping  sickness,  and  the 
hookworm  disease.  Animals  also  carry  disease,  especially  the 
flies  and  mosquitoes ;  rats  and  olj^ier  animals  are  also  well  known 
as  spreaders  of  disease. 

From  a  money  standpoint,  animals  called  insects  do  much  harm. 
It  is  estimated  that  in  this  country  alone  they  are  annually  re- 
sponsible for  $800,000,000  worth  of  damage  by  eating  crops,  forest 
trees,  stored  food,  and  other  material  wealth. 

The  Uses  of  Animals  to  Man.  —  We  all  know  the  uses  man 
has  made  of  the  domesticated  animals  for  food  and  as  beasts  of 
burden.  But  many  other  uses  are  found  for  animal  products, 
and  materials  made  from  animals.  Wool,  furs,  leather,  hides, 
feathers,  and  silk  are  examples.  The  arts  make  use  of  ivory,  tor- 
toise shell,  corals,  and  mother-of-pearl ;  from  animals  come  per- 
fumes and  oils,  glue,  lard,  and  butter;  animals  produce  honey, 
wax,  milk,  eggs,  and  various  other  commodities. 

The  Conservation  of  our  Natural  Resources.  —  Still  another 
reason  why  we  should  study  biology  is  that  we  may  work  under- 
standingly  for  the  conservation  of  our  natural  resources,  especially 
of  our  forests.  The  forest,  aside  from  its  beauty  and  its  health- 
giving  properties,  holds  water  in  the  earth.  It  keeps  the  water 
from  drying  out  of  the  earth  on  hot  days  and  from  running  off  on 
rainy  days.  Thus  a  more  even  supply  of  water  is  given  to  our 
rivers,  and  thus  freshets  are  prevented.  Countries  that  have  been 
deforested,  such  as  China,  Italy,  and  parts  of  France,  are  now  sub- 
ject to  floods,~^nd  are  in  many  places  barren.  On  the  forests 
depend  our  supply  of  timber,  our  future  Avater  power,  and  the 
future  commercial  importance  of  cities  which,  like  New  York,  are 
located  at  the  mouths  of  our  navigable  rivers. 

HUNTER.  CIV.   BI. — 2 


18        SOME  REASONS   FOR  STUDYING   BIOLOGY 

Plants  and  Animals  mutually  Helpful.  —  Most  plants  and  ani- 
mals stand  in  an  attitude  of  mutual  helpfulness  to  one  another, 
plants  providing  food  and  shelter  for  animals ;  animals  giving  off 
waste  materials  useful  to  plants  in  the  making  of  food.  We  also 
learn  that  plants  and  animals  need  the  same  conditions  in  their 
surroundings  in  order  to  live  :  water,  air,  food,  a  favorable  temper- 
ature, and  usually  light.  The  life  processes  of  both  plants  and 
animals  are  essentially  the  same,  and  the  living  matter  of  a  tree  is 
as  much  alive  as  is  the  living  matter  in  a  fish,  a  dog,  or  a  man. 

Biology  in  its  Relation  to  Society.  —  Again,  the  study  of  biology 
should  be  part  of  the  education  of  every  boy  and  girl,  because  so- 
ciety itself  is  founded  upon  the  principles  which  biology  teaches. 
Plants  and  animals  are  living  things,  taking  what  they  can  from 
their  surroundings ;  they  enter  into  competition  with  one  another, 
and  those  which  are  the  best  fitted  for  life  outstrip,  the  others. 
Animals  and  plants  tend  to  vary  each  from  its  nearest  relative  in  all 
details  of  structure.  The  strong  may  thus  hand  down  to  their 
offspring  the  characteristics  which  make  them  the  winners.  Health 
and  strength  of  body  and  mind  are  factors  which  tell  in  winning. 

Man  has  made  use  of  this  message  of  nature,  and  has  developed 
improved  breeds  of  horses,  cattle,  and  other  domestic  animals. 
Plant  breeders  have  likewise  selected  the  plants  or  seeds  that  have 
varied  toward  better  plants,  and  thus  have  stocked  the  earth  with 
hardier  and  more  fruitful  domesticated  plants.  Man's  dominion 
over  the  living  things  of  the  earth  is  tremendous.  This  is  due  to  his 
understanding  the  principles  which  underlie  the  science  of  biology. 

Finally  the  study  of  biology  ought  to  make  us  better  men 
and  women  by  teaching- us  that  unselfishness  exists  in  the  natural 
world  as  well  as  among  the  highest  members  of  society.  Ani- 
mals, lowly  and  complex,  sacrifice  their  comfort  and  their  very 
lives  for  their  young.  In  the  insect  communities  the  welfare  of 
the  individual  is  given  up  for  the  best  interests  of  the  community. 
The  law  of  mutual  give  and  take,  of  sacrifice  for  the  common  good, 
is  seen  everywhere.  This  should  teach  us,  as  we  come  to  take  our 
places  in  society,  to  be  willing  to  give  up  our  individual  pleasure/ 
or  selfish  gain  for  the  good  of  the  community  in  which  we  livjB. 
Thus  the  application  of  biological  principles  will  benefit  society. 


11.   THE   ENVIRONMENT   OF   PLANTS   AND   ANIMALS 


Problem,  —  To  discover  some  of  tlie  factors  of  the  environ- 
ment of  plants  and  animals. 
(a)  Environment  of  a  plant. 
ib)  Environment  of  an  animal. 
(c)  Hojne  environment  of  a  girl  or  boy. 

Laboratory  Suggestions 

Laboratory  demonstrations.  —  Factors  of  the  environment  of  a  living 
plant  or  animal  in  the  vivarium. 

Home  exercise.  —  The  study  of  the  factors  making  up  my  own  environ- 
ment and  how  I  can  aid  in  their  control. 

Environment.  —  Each  one  of  us,  no  matter  where  he  Hves,  comes 
in  contact  with  certain  surroundings.     Air  is  everywhere  around 

us ;  light  is  necessary  to  us,  so  much  so 
that  we  use  artificial  light  at  night.     The 
city  street,  with  its  dirty  and  hard  paving 
stones,  has  come  to  take  the 
place  of  the  soil  of  the  village 
or  farm.     Water  and  food  are 
a  necessary  part  of  our  sur- 
roundings.     Our  clothing, 
useful  to  maintain  a  certain 
temperature,  must  also  be 
included.     All  these  things 
—  air,  light,  heat,  water,  food  —  together 
make  up  our  environment. 

All  other  animals,   and  all  plants   as 
well,  are  surrounded  by  and  use  prac- 
tically the  same  things  from   their  en- 
vironment as  we  do.     The  potted  plant 
in  the  window,  the  goldfish  in  the  aquarium,  your  pet  dog  at 
home,  all  use,  as  we  will  later  prove,  the  factors  of  their  environ- 

19 


An  unfavorable  city  environ- 
ment. 


20       ENVIRONMENT  OF   PLANTS   AND  ANIMALS 


ment  in  the  same  manner.  Air,  water,  light,  a  certain  amount  of 
heat,  soil  to  live  in  or  on,  and  food  form  parts  of  the  surroundings 
of  every  living  thing. 

The  Same  Elements  found  in  Plants 
and  Animals  as  in  their  Environment. 
—  It  has  been  found  by  chemists  that 
the  plants  and  animals  as  well  as  their 
environment  may  be  reduced  to  about 
eighty  very  simple  substances  known 
as  chemical  elements.  For  example, 
the  air  is  made  up  largely  of  two  ele- 
ments, oxygen  and  nitrogen.  Water, 
by  means  of  an  electric  current,  may 
be  broken  up  into  two  elements,  oxygen 
and  hydrogen.  The  elements  in  water 
are  combined  to  make  a  cheynical  com- 
poimd.  The  oxygen  and  nitrogen  of 
the  air  are  not  so  united,  but  exist  as 
separate  gases.     If  we  were  to  study 


1 

An  experiment  that  shows  the 
air  contains  about  four  fifths 
nitrogen. 


Apparatus  for  separating 
water  by  means  of  an 
electric  current  into  the 
two  elements,  hydrogen 
and  oxygen. 


the  chemistry  of  the  bodies  of  plants  and  animals  and  of  their 
foods,  we  would  find  them  to  be  made  up  of  certain  chemical 
elements  combined  in  various  complex  compounds.  These  ele- 
ments are  principally  carbon,  hydrogen,  oxygen,  nitrogen,  and 
perhaps  a  dozen  others  in  very  minute  proportions.  But  the 
same  elements  present  in  the  living  things  might  also  be  found 


ENVIRONMENT  OF  PLANTS  AND  ANIMALS       21 


SULPHUR 

PHOSPHORU5I 
CALCIUM 


NITROGEN 
3.7s  Iks. 


0.031U  %,o% 
0  SiGXts.  y-jir 


HYDROGEN 

I3.65\bs. 

9.1^ 


CARBON 

13.5^ 


OXYGEN 

I08.l5lb5. 


in  the  environment,  for  example,  water,  food,  the  air,  and  the  soil. 
It  is  logical  to  believe  that  living  things  use  the  chemical  elements 
in  their  surroundings  and  in  some  won- 
derful manner  build  up  their  own  bodies 
from  the  materials  found  in  their  en- 
vironment. How  this  is  done  we  will 
learn  in  later  chapters. 

What  Plants  and  Animals  take  from 
their  Environment.  Air.  —  It  is  a  self- 
evident  fact  that  animals  need  air. 
Even  those  living  in  the  water  use  the 
air  dissolved  in  the  water.  A  fish 
placed  in  an  air-tight  jar  will  soon  die. 
It  will  be  proven  later  that  plants  also 
need  air  in  order  to  live. 

Water.  —  We  all  know  that  water 
must  form  part  of  the  environment  of 
plants  and  animals.  It  is  a  matter  of 
common  knowledge  that  pets  need 
water  to  drink;  so  do  other  animals. 
Every  one  knows  we  must  water  a 
potted  plant  if  we  expect  it  to  grow. 
Water  is  of  so  much  importance  to  man 
that  from  the  time  of  the  Caesars  until 
now  he  has  spent  enormous  sums  of  money  to  bring  pure  water 
to  his  cities.  The  United  States  government  is  spending  millions 
of  dollars  at  the  present  time  to  bring  by  irrigation  the  water 
needed  to  support  life  in  the  western  desert  lands. 

Light  as  Condition  of  the  Environment.  —  Light  is  another  im- 
portant factor  of  the  environment.  A  study  of  the  leaves  on  any 
green  plant  growing  near  a  window  will  convince  one  that  such 
plants  grow  toward  the  light.  All  green  plants  are  thus  influenced 
by  the  sun.  Other  plants  which  are  not  green  seem  either  indif- 
ferent or  are  negatively  influenced  (move  away  from)  the  source 
of  light.  Animals  may  or  may  not  be  attracted  by  light.  A 
moth,  for  example,  will  fly  toward  a  flame,  an  earthworm  will 
move  away  from  light.     Some   animals   prefer   a   moderate    or 


<f^ 


Chart  to  show  the  percentage 
of  chemical  elements  in  the 
human  body. 


22       ENVIRONMENT  OF  PLANTS   AND  ANIMALS 


TliL'  effect  of  water  upon  the  growth  of  trees.  These  trees  were  all  planted  at  the 
same  time  in  soil  that  is  sandy  and  uniform.  They  are  watered  by  a  small 
stream  which  runs  from  left  to  right  in  the  picture.  Most  of  the  water  soaks 
into  the  ground  before  reaching  the  last  trees. 


weak   intensity    of   light  and    live  in  shady  forests  or  jungles, 
prowling  about  at  night.     Others  seem  to  need  much  and  strong 

light.  And  man  himself 
enjoys  only  moderate  in- 
tensity of  light  and  heat. 
Look  at  the  shady  side  of 
a  city  street  on  any  hot 
day  to  prove  this  state- 
ment. 

Heat.  —  Animals  and 
plants  are  both  affected 
by  heat  or  the  absence  of 
it.  In  cold  weather  green 
plants  either  die  or  their 
life  activities  are  temporarily  suspended,  —  the  plant  becomes 
dormant.  Likewise  small  animals,  such  as  insects,  may  be  killed 
by  cold  or  they  may  hibernate  under  stones  or  boards.  Their 
life  activities  are  stilled  until  the  coming  of  warm  weather.     Bears 


The  effect  of  light  upon  a  growing  plant. 


ENVIRONMENT  OF  PLANTS  AND  ANIMALS      23 

and  other  large  animals  go  to  sleep  during  the  winter  and  awake 
thin  and  active  at  the  approach  of  warm  weather.  Animals  or 
plants  used  to  certain  temperatures  are  killed  if  removed  from 
those  temperatures.  Even  man,  the  most  adaptable  of  all  ani- 
mals, cannot  stand  great  changes  without  discomfort  and  some- 
times death.  He  heats  his  houses  in  winter  and  cools  them  in 
summer  so  as  to  have  the  amount  of  heat  most  acceptable  to  him, 
i.e.  about  70°  Fahrenheit. 

The  Environment  determines  the  Kind  of  Animals  and  Plants 
within  It.  —  In  our  study  of  geography  we  learned  that  certain 


Vegetation  in  Northern  Russia.     The  trees  in  this  picture  are  nearly  one  hundred 
years  old.     They  live  under  conditions  of  extreme  cold  most  of  the  year. 


luxuriant  growths  of  trees  and  climbing  plants  were  characteristic 
of  the  tropics  with  its  moist,  warm  climate.  No  one  would  expect 
to  find  living  there  the  hardy  stunted  plants  of  the  arctic  region. 
Nor  would  we  expect  to  find  the  same  kinds  of  animal  life  in  warm 
regions  as  in  cold.  The  surroundings  determine  the  kind  of  living 
things  there.  Plants  or  animals  fitted  to  live  in  a  given  locality 
will  probably  be  found  there  if  they  have  had  an  opportunity  to 


24       ENVIRONMENT  OF  PLANTS   AND  ANIMALS 

reach  that  locality.  If,  for  example,  temperate  forms  of  life  were 
introduced  by  man  into  the  tropics,  they  would  either  die  or  they 
would  gradually  change  so  as  to  become  fitted  to  live  in  their  new 
environment.  Sheep  with  long  wool  fitted  to  live  in  England, 
when  removed  to  Cuba,  where  conditions  of  greater  heat  exist. 


Plant  life  in  a  moist  tropical  forest.     Notice  the  air  plants  to  the  left  and  the 

resurrection  ferns  on  the  tree  trunk. 

soon  died  because  they  were  not  fitted  or  adapted  to  live  in  their 
changed  environment. 

Adaptations.  —  Plants  and  animals  are  not  only  fitted  to  live 
under  certain  conditions,  but  each  part  of  the  body  may  be  fitted  to 
do  certain  work.  I  notice  that  as  I  write  these  words  the  fingers 
of  my  right  hand  grasp  the  pen  firmly  and  the  hand  and  arm  exe- 
cute some  very  complicated  movements.  This  they  are  able  to 
do  because  of  the  free  movement  given  through  the  arrangement 
of  the  delicate  bones  of  the  wrist  and  fingers,  their  attachment 
to  the  bones  of  the  arm,  a  wonderful  complex  of  muscles  which 
move  the  bones,  and  a  directing  nervous  system  which  plans 
the  work.     Because  of  the  peculiar  fitness  in  the  structure  of  the 


FmrERTY  UBRART 


ENVIRONMENT  OF  PLANTS  AND  ANIMALS      25 


hand  for  this  work  we  say  it  is  adapted  to  its  function  of  grasping 
objects.  Each  part  of  a  plant  or  animal  is  usually  fitted  for  some 
particular  work.  The  root  of  a  green  plant,  for  example,  is  fitted 
to  take  in  water  by  having  tiny  absorbing  organs  growing  from  it, 
the  stems  have  pipes  or  tubes  to  convey  liquids  up  and  down  and 
are  strong  enough  to  support  the  leafy  part  of  the  plant.  Each 
part  of  a  plant  does  work,  and  is  fitted,  by  means  of  certain  struc- 
tures, to  do  that  work.  It  is  because  of  these  adaptations  that 
living  things  are  able  to  do  their  work  within  their  particular  en- 
vironment. 

Plants  and  Animals  and  their  Natural  Environment.  —  Those 
of  us  who  have  tried  to  keep  potted  plants  in  the  schoolroom 
know  how  difficult  it  is  to  keep  them  healthy.  Dust,  foreign 
gases  in  the  air,  lack  of  moisture,  and  other  causes  make  the 
artificial  environment  in  which  they  are  placed  unsuitable  for 
them. 

A  goldfish  placed  in  a  small  glass  jar  with  no  food  or  no  green 
water  plants  soon  seeks 
the  surface  of  the  water, 
and  if  the  water  is  not 
changed  frequently  so  as 
to  supply  air  the  fish  will 
die.  Again  the  artificial 
environment  lacks  some- 
thing that  the  fish  needs. 
Each  plant  and  animal  is 
limited  to  a  certain  en- 
vironment because  of  cer- 
tain individual  needs  which 
make  the  surroundings  fit 
for  it  to  live  in. 

Changes  in  Environ- 
ment. —  Most  plants  and 
animals  do  not  change 
their  environment.  Trees, 
green  plants  of  all  kinds,  ^  ^^^^^^j  ^^^^.^^  ^^^  ^  ^t,^^,,,  No  trout 
and   some  animals  remain        would  be  found  above  this  fall,     why  not? 


26       ENVIRONMENT  OF  PLANTS  AND  ANIMALS 


fixed  in  one  spot  practically  all  their  lives.  Certain  tiny  plants 
and  most  animals  move  from  place  to  place,  either  in  air,  water, 
on  the  earth  or  in  the  earth,  but  they  maintain  relatively  the 
same  conditions  in  environment.  Birds  are  perhaps  the  most 
striking  exception,  for  some  may  fly  thousands  of  miles  from 
their  summer  homes  to  winter  in  the  south.  Other  animals,  too, 
migrate  from  place  to  place,  but  not  usually  where  there  are 
great  changes  in  the  surroundings.  A  high  mountain  chain  with 
intense  cold  at  the  upper  altitudes  would  be  a  barrier  over  which,  for 
example,  a  bear,  a  deer,  or  a  snail  could  not  travel.  Fish  like  trout 
will  migrate  up  a  stream  until  they  come  to  a  fall  too  high  for  them 
to  jump.  There  they  must  stop  because  their  environment  limits 
them. 

Man  in  his  Environment.  —  Man,  while  he  is  like  other  animals 
in  requiring  heat,  light,  water,  and  food,  differs  from  them  in  that 

he  has  come  to  live  in  a 
more  or  less  artificial  en- 
vironment. Men  who 
lived  on  the  earth  thou- 
sands of  year  ago  did  not 
wear  clothes  or  have  elab- 
orate homes  of  wood  or 
brick  or  stone.  They  did 
not  use  fire,  nor  did  they 
eat  cooked  foods.  In 
short,  by  slow  degrees, 
civilized  man  has  come  to 
live  in  a  changed  environ- 
ment from  that  of  other 
animals.  The  living  to- 
gether of  men  in  com- 
munities has  caused  cer- 
tain needs  to  develop. 
,   ,  ,  Many  things  can  be  sup- 

A  new  apartment  house,  with  out-ot-door  ,.     i  . 

sleeping  porch.  plied  m  common,  as  water, 

milk,  foods.     Wastes  of  all 
kinds  have  to  be  disposed  of  in  a  town  or  city.     Houses  have  come 


ENVIRONMENT  OF   PLANTS  AND  ANIMALS       27 

to  be  placed  close  together,  or  piled  on  top  of  each  other,  as  in  the 
modern  apartment.  Fields  and  trees,  all  outdoor  life,  has  practi- 
cally disappeared.  Man  has  come  to  live  in  an  artificial  envi- 
ronment. 

Care  and  Improvement  of  One's  Environment.  —  Man  can 
modify  or  change  his  surroundings  by  making  this  artificial  en- 
vironment favorable  to  live  in.  He  may  heat  his  dwellings  in 
winter  and  cool  them  in  summer  so  as  to  maintain  a  moderate  and 
nearly  constant  temperature.  He  may  see  that  his  dwellings  have 
windows  so  as  to  let  light  and  air  pass  in  and  out.  He  may  have 
light  at  night  and  shade  by  day  from  intense  light.  He  may  have 
a  system  of  pure  water  supply  and  may  see  that  drains  or  sewers 
carry  away  his  wastes.  He  may  see  to  it  that  people  ill  with 
'*  catching  "  or  infectious  diseases  are  isolated  or  quarantined  from 
others.  This  care  of  the  artificial  environment  is  known  as  sanita- 
tion, while  the  care  of  the  individual  for  himself  within  the  environ- 
ment is  known  as  hygiene.  It  will  be  the  chief  end  of  this  book  to 
show  girls  and  boys  how  they  may  become  good  citizens  through 
the  proper  control  of  personal  hygiene  and  sanitation. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Hough  and  Sedgwick,  Elements  of  Hygiene  and  Sanitation.     Ginn  and  Company. 
Jordan  and  Kellogg,  Animal  Life.     Appleton. 

Sharpe,  A  Laboratory  Manual  for  the  Solution  of  Problems  in  Biology,  p.  95.     Amer- 
ican Book  Company. 
Tolman,  Hygiene  for  the  Worker.    American  Book  Company. 

ADVANCED 

Allen,  Civics  and  Health.     Ginn  and  Company. 


III.   THE  INTERRELATIONS  OF  PLANTS  AND  ANIMALS 

Problem,  —  To  discover  the  general  interrelations  of  green 
plants  and  animals. 

{a)  Plants  as  homes  for  insects. 

(b)  Plants  as  food  for  insects. 

(c)  Insects  as  pollinating  agents. 

Laboratory  Suggestions 

A  field  trip:  —  Object :  to  collect  common  insects  and  study  their  gen- 
eral characteristics ;  to  study  the  food  and  shelter  relation  of  plant  and 
insects.  The  pollination  of  flowers  should  also  be  carefully  studied  so  as 
to  give  the  pupil  a  general  viewpoint  as  an  introduction  to  the  study  of 
biology. 

Laboratory  exercise.  —  Examination  of  simple  insect,  identification  of 
parts  —  drawing.  Examination  and  identification  of  some  orders  of 
insects. 

Laboratory  demonstration.  —  Life  history  of  monarch  and  some  other 
butterflies  or  moths. 

Laboratory  exercise.  —  Study  of  simple  flower  —  emphasis  on  work  of 
essential  organs,  drawing. 

Laboratory  exercise.  —  Study  of  mutual  adaptations  in  a  given  insect 
and  a  given  flower,  e.g.  butter  and  eggs  and  bumble  bee. 

Demonstration  of  examples  of  insect  pollination. 

The  Object  of  a  Field  Trip.  —  Many  of  us  live  in  the  city,  where 
the  crowded  streets,  the  closely  packed  apartments,  and  the  city 
playgrounds  form  our  environment.  It  is  very  artificial  at  best. 
To  understand  better  the  normal  environment  of  plants  or  animals 
we  should  go  into  the  country.  Failing  in  this,  an  overgrown  city 
lot  or  a  park  will  give  us  much  more  closely  the  environment  as  it 
touches  some  animals  lower  than  man.  We  must  then  remember 
that  in  learning  something  of  the  natural  environment  of  other 
living  creatures  we  may  better  understand  our  own  environment 
and  our  relation  to  it. 

28 


INTERRELATIONS   OF   PLANTS   AND  ANIMALS     29 


On  any  bright  warm  day  in  the  fall  we  will  find  insects  swarming 
everywhere  in  any  vacant  lot  or  the  less  cultivated  parts  of  a  city 
park.  Grasshoppers,  butterflies  alighting  now  and  then  on  the 
flowers,  brightly  marked  hornets,  bees  busily  working  over  the 
purple  asters  or  golden  rod,  and  many  other  forms  hidden  away 
on  the  leaves  or  stems  of  plants  may  be  seen.  If  we  were  to  select 
for  observation  some  partially  decayed  tree,  we  would  find  it  also 
inhabited.  Beetles  would  be  found  boring  through  its  bark  and 
wood,  while  caterpillars  (the  young  stages  of  butterflies  or  moths) 
are  feeding  on  its  leaves  or  building  homes  in  its  branches.  Every- 
where above,  on,  and  under  ground  may  be  noticed  small  forms  of 
life,  many  of  them  insects.  Let  us  first  see  how  we  would  go  to 
work  to  identify  some  of  the  common  forms  we  would  be  likely  to 
find  on  plants.  Then  a  little  later  we  will  find  out  what  they  are 
doing  on  these  plants. 

How  to  tell  an  Insect.  —  A  bee  is  a  good  example  of  the  group 
of  animals  we  call  insects.  If  we  examine  its  body  carefully,  we 
notice  that  it  has  three  regions,  a 
front  part  or  head,  a  middle  part 
called  the  thorax,  and  a  hind  portion, 
jointed  and  hairy,  the  abdomen.  We 
cannot  escape  noting  the  fact  that  this 
insect  has  wings  with  which  it  flies 
and  that  it  also  has  legs.  The  three 
pairs  of  legs,  which  are  jointed  and 
provided  with  tiny  hooks  at  the  end, 
are  attached  to  the  thorax.  Two 
pairs  of  delicate  wings  are  attached 
to  the  upper  or  dorsal  side  of  the 
thorax.  The  thorax  and  indeed  the 
entire  body,  is  covered  with  a  hard 
shell  of  material  similar  to  a  cow's 
horn,  there  being  no  skeleton  inside  for 
the  attachment  of  muscles.  If  we 
carefully  watch    the    abdomen   of   a 

living  bee,  we  notice  it  move  up  and  down  quite  regularly.     The 
animal  is  breathing  through  tiny  breathing  holes  called  spiracles. 


An  insect  viewed  from  the  side. 
Notice  the  head,  thorax,  and 
abdomen.  What  other  char- 
acters do  you  find  ? 


30    INTERRELATIONS   OF  PLANTS  AND  ANIMALS 

placed  along  the  side  of  the  thorax  and  abdomen.     Bees  also  have 
compound  eyes.     Wings  are  not  found  on  all  insects,  but  all  the 

other  characters  just  given  are  marks  of  the 
great  group  of  animals  we  call  insects. 

Forms  to  be  looked  for  on  a  Field  Trip.  — 

Inasmuch  as  there  are  over  360,000  different 

species  or  kinds  of  insects,  it  is  evident  that  it 

would  be  a  hopeless  task  for  us  even  to  think  of 

recognizing  all  of  them.     But  we  can  learn  to 

^pound  eye^  of  ^an  recognize  a  few  examples  of  the  common  forms 

insect  (highly  mag-  that  might  be  met  on  a  field  trip.     In  the  nei'ds, 

^   ^  ■  on  grass,  or  on  flowering  plants  we  may  count  on 

finding  members  from  six  groups  or  orders  of  insects.     These  may 

be  kno^vn  by  the  following  characters. 

The  order  Hymenoptera  (membrane  wing)  to  which  the  bees, 
wasps,  and  ants  belong  is  the  only  insoct  group  the  members  of 
which  are  provided  with  true  stings.  This  sting  is  placed  in  a 
sheath  at  the  extreme  hind  end  of  the  abdomen.  Other  charac- 
teristics, which  show  them  to  be  insects,  have  been  given  above. 

Butterflies  or  moths  will  be  found  hovering  over  flowers.  They 
belong  to  the  order  Lepidoptera  (scale  wings).  This  name  is 
given  to  them  because  their  wings  are  covered  with  tiny  scales, 
which  fit  into  little  sockets  on  the  wing  much  as  shingles  are  placed 
on  a  roof.  The  dust  which  comes  off  on  the  fingers  when  one 
catches  a  butterfly  is  composed  of  these  scales.  The  wings  are 
always  large  and  usually  brightly  colored,  the  legs  small,  and  one 
pair  is  often  inconspicuous.  These  insects  may  be  seen  to  take 
liquid  food  through  a  long  tubelike  organ,  called  the  proboscis, 
which  they  keep  rolled  up  under  the  head  when  not  in  use.  The 
young  of  the  butterfly  or  moth  are  known  as  caterpillars  and  feed 
on  plants  by  means  of  a  pair  of  hard  jaws. 

Grasshoppers,  found  almost  everywhere,  and  crickets,  black 
grasshopper-like  insects  often  found  under  stones,  belong  to  the 
order  Orthoptera  (straight  wings).  Members  of  this  group  may 
usually  be  distinguished  by  their  strong,  jumping  hind  legs,  by 
their  chewing  or  biting  mouth  parts,  and  by  the  fact  that  the  hind 
wings  are  folded  up  under  the  somewhat  stiffer  front  wings. 


INTERRELATIONS  OF  PLANTS  AND  ANIMALS    31 


Another  group  of  insects  sometimes  found  on  flowers  in  the  fall 
are  flies.  They  belong  to  the  order  Diptera  (two  wings).  These 
insects  are  usually  rather  small  and  have  a  single  pair  of  gauzy 


Forms  of  life  to  be  met  on  a  field  trip.  A,  The  red-legged  locust,  one  of  the 
Orthoptera;  o,  the  egg-layer,  about  natural  size.  B,  the  honey  bee,  one  of 
the  Htjmenovtera,  about  natural  size.  C,  a  bug,  one  of  the  Heyniptera,  about 
natural  size.  D,  a  butterfly,  an  example  of  the  Lepidoptera,  slightly  reduced. 
E,  a  house  fly,  an  example  of  the  Diptera,  about  twice  natural  size.  F,  an 
orb-weaving  spider,  about  half  natural  size.  (This  is  not  an  insect,  note  the 
number  of  legs.)     G,  a  beetle,  slightly  reduced,  one  of  the  Coleoptera. 


32    INTERRELATIONS  OF   PLANTS  AND  ANIMALS 

wings.  Flies  are  of  much  importance  to  man  because  certain  of 
their  number  are  disease  carriers. 

Bugs,  members  of  the  order  Hemiptera  (half  wings),  have  a 
jointed  proboscis  which  points  backward  between  the  front  legs. 
They  are  usually  small  and  may  or  may  not  have  wings. 

The  beetles  or  Coleoptera  (sheath  wings),  often  mistaken  for 
bugs  by  the  uneducated,  have  the  first  pair  of  hardened  wings 
meeting  in  a  straight  line  in  the  middle  of  the  back,  the  second 
pair  of  wings  being  covered  by  them.  Beetles  are  frequently  found 
on  goldenrod  blossoms  in  the  fall. 

Other  forms  of  life,  especially  spiders,  which  have  four  pairt-j  of 
walking  legs,  centipedes  and  millepedes,  both  of  which  are  worm- 
like and  have  many  pairs  of  legs,  may  be  found. 

Try  to  discover  members  of  the  six  different  orders  named 
above.  Collect  specimens  and  bring  them  to  the  laboratory  for 
identification. 

Why  do  Insects  live  on  Plants?  —  We  have  found  insect  life 
abundant  on  living  green  plants,  some  visiting  flowers,  others 
hidden  away  on  the  stalks  or  leaves  of  the  plants.  Let  us  next 
try  to  find  out  why  insects  live  among  and  upon  flowering  green 
plants. 

The  Life  History  of  the  Milkweed  Butterfly.  —  If  it  is  possible 
to  find  on  our  trip  some  growing  milkweed,  we  are  quite  likely  to 
find  hovering  near,  a  golden  brown  and  black  butterfly,  the  monarch 
or  milkweed  butterfly  {Anosia  plexippus).  Its  body,  as  in  all 
insects,  is  composed  of  three  regions.  The  monarch  frequents 
the  milkweed  in  order  to  lay  eggs  there.  This  she  may  be  found 
doing  at  almost  any  time  from  June  until  September. 

Egg  and  Larva.  —  The  eggs,  tiny  hat-shaped  dots  a  twentieth  of 
an  inch  in  length,  are  fastened  singly  to  the  underside  of  milkweed 
leaves.  Some  wonderful  instinct  leads  the  animal  to  deposit  the 
eggs  on  the  milkweed,  for  the  young  feed  upon  no  other  plant. 
The  eggs  hatch  out  in  four  or  five  days  into  rapid-growing  worm- 
like caterpillars,  each  of  which  will  shed  its  skin  several  times 
before  it  becomes  full  size.  These  caterpillars  possess,  in  addition 
to  the  three  pairs  of  true  legs,  additional  pairs  of  prolegs  or  cater- 
pillar legs.     The  animal  at  this  stage  is  known  as  a  larva. 


INTERRELATIONS  OF  PLANTS  AND  ANIMALS    33 


Formation  of  Pupa.  —  After  a  life  of  a  few  weeks  at  most,  the 
caterpillar  stops  eating  and  begins  to  spin  a  tiny  mat  of  silk  upon 
a  leaf  or  stem.  It  attaches  itself  to  this  web  by  the  last  pair  of 
prolegs,  and  there  hangs  in  the  dormant  stage  known  as  the 
chrysalis  or  pupa.  This  is  a  resting  stage  during  which  the  body 
changes  from  a  cater- 
pillar to  a  butterfly. 

The  Adult.  —  After 
a  week  or  more  of 
inactivity  in  the  pupa 
state,  the  outer  skin 
is  split  along  the 
back,  and  the  adult 
butterfly  emerges.  At 
first  the  wings  are  soft 
and  much  smaller 
than  in  the  adult. 
Within  fifteen  minutes 
to  half  an  hour  after 
the  butterfly  emerges, 
however,  the  wings 
are  full-sized,  having 
been  pumped  full  of 
blood  and  air,  and  the 
little  insect  is  ready 
after  her  wedding  flight 
to  follow  her  instinct 
to  deposit  her  eggs  on 
a  milkweed  plant. 

Plants  furnish  Insects  with  Food.  —  Food  is  the  most  important 
factor  of  any  animal's  environment.  The  insects  which  we  have 
seen  on  our  field  trip  feed  on  the  green  plants  among  which  they 
live.  Each  insect  has  its  own  particular  favorite  food  plant  or 
plants,  and  in  many  cases  the  eggs  of  the  insect  are  laid  on  the 
food  plant  so  that  the  young  may  have  food  close  at  hand.  Some 
insects  prefer  the  rotted  wood  of  trees.  An  American  zoologist, 
Packard,  has  estimated  that  over  450  kinds  of  insects  live  upon 

HUNTER,    CIV.   BI. — 3 


Monarch  butterfly:  adults,  larvse,  and  pupa  on  their 
food  plant,  the  milkweed.  (From  a  photograph 
loaned  by  the  American  Museum  of  Natural 
History.) 


34     INTERRELATIONS   OF  PLANTS   AND  ANIMALS 


Damage  done  by  insects.     These  trees  have 
been  killed  by  boring  insects. 


oak  trees  alone.    Everywhere  animals  are  engaged  in  taking  their 
nourishment  from  plants,  and  millions  of  dollars  of  damage  is  done 

every  year  to  gardens, 
fruits,  and  cereal  crops 
by  insects. 

All  Animals  depend  on 
Green  Plants. — But  in- 
sects in  their  turn  are  the 
food  of  birds ;  cats  and 
dogs  may  kill  birds  ;  lions 
or  tigers  live  on  still  larger 
defenseless  animals  as  deer 
or  cattle.  And  finally 
comes  man,  who  eats  the 
bodies  of  both  plants  and 
animals.  But  if  we  reduce 
this  search  after  food  to  its  final  limit,  we  see  that  green  plants 
provide  all  the  food  for  animals.  For  the  lion  or  tiger  eats  the 
deer  which  feeds  upon  grass  or  green  shoots  of  young  trees,  or 
the  cat  eats  the  bird  that  lives  on  weed  seeds.  Green  plants 
supply  the  food  of  the  world.  Later  by  experiment  we  will  prove 
this. 

Homes  and  Shelter.  —  After  a  field  trip  no  one  can  escape  the 
knowledge  that  plants  often  give  animals  a  home.  The  grass 
shelters  millions  of  grasshoppers  and  countless  hordes  of  other  small 
insects  which  can  be  obtained  by  sweeping  through  the  grass  with 
an  insect  net.  Some  insects  build  their  homes  in  the  trees  or 
bushes  on  which  they  feed,  while  others  tunnel  through  the  wood, 
making  homes  there.  Spiders  build  webs  on  plants,  often  using 
the  leaves  for  shelter.  Birds  nest  in  trees,  and  many  other  wild 
animals  use  the  forest  as  their  home.  Man  has  come  to  use  all 
kinds  of  plant  products  to  aid  him  in  making  his  home,  wood  and 
various  fibers  being  the  most  important  of  these. 

What  do  Animals  do  for  Plants  ?  —  So  far  it  has  seemed  that 
green  plants  benefit  animals  and  receive  nothing  in  return.  We 
will  later  see  that  plants  and  animals  together  form  a  balance  of  life 
on  the  earth  and  that  one  is  necessary  for  the  other.     Certain 


INTERRELATIONS   OF   PLANTS   AND  ANIMALS    35 


substances  found  in  the  body  wastes  from  animals  are  necessary 
to  the  life  of  a  green  plant. 

Insects  and  Flowers.  —  Certain  other  problems  can  be  worked 
out  in  the  fall  of  the  year.  One  of  these  is  the  biological  interre- 
lations between  insects  and  flowers.  It  is  easy  on  a  field  trip  to 
find  insects  lighting  upon  flowers.  They  evidently  have  a  reason 
for  doing  this.  To  find  out  why  they  go  there  and  what  they  do 
when  there,  it  will  be  first  necessary 
for  us  to  study  flowers  with  the  idea 
of  finding  out  what  the  insects  get 
from  them,  and  what  the  flowers 
get  from  the  insects. 

The  Use  and  Structure  of  a 
Flower.  —  It  is  a  matter  of  common 
knowledge  that  flowers  form  fruits 
and  that  fruits  contain  seeds.  They 
are,  then,  very  important  parts  of 
certain  plants.  Our  field  trip  shows 
us  that  flowers  are  of  various  shapes, 
colors,  and  sizes.  It  will  now  be 
our  problem  first  to  learn  to  know 
the  parts  of  a  flower,  and  then  find 
out  how  they  are  fitted  to  attract 
and  receive  insect  visitors. 

The  Floral  Envelope.  —  In  a 
flower  the  expanded  portion  of  the 
flower  stalk,  which  holds  the  parts 
of  the  flower,  is  called  the  receptacle. 
The  green  leaflike  parts  covering  the 
unopened  flower  are  called  the  sepals. 
Together  they  form  the  calyx. 

The  more  brightly  colored  structures 
are  the  petals.  Together  they  form 
the  corolla.  The  corolla  is  of  importance,  as  we  shall  see  later, 
in  making  the  flower  conspicuous.  Frequently  the  |)etals  or 
corolla  have  bright  marks  or  dots  which  lead  down  to  the  base  of 
the  cup  of  the  flower,  where  a  sweet  fluid  called  nectar  is  made  and 


A  section  of  a  flower,  cut  lengthwise. 
In  the  center  find  the  pistil  with 
the  ovary  containing  a  number  of 
ovules.  Around  this  organ  notice 
a  circle  of  stalked  structured,  the 
stamens;  the  knobs  at  tlie  end 
contain  pollen.  The  outer  circles 
of  parts  arc  called  the  petals  and 
sepals,  as  we  go  from  the  inside 
outward. 


36     INTERRELATIONS   OF   PLANTS  AND  ANIMALS 

secreted.  It  is  principally  this  food  substance,  later  made  into 
honey  by  bees,  that  makes  flowers  attractive  to  insects. 

The  Essential  Organs.  —  A  flower,  however,  could  live  without 
sepals  or  petals  and  still  do  the  work  for  which  it  exists.  Certain 
essential  organs  of  the  flower  are  within  the  so-called  floral  envelope. 
They  consist  of  the  stamens  and  pistil,  the  latter  being  in  the  center 
of  the  flower.  The  structures  with  the  knobbed  ends  are  called 
stamens.  In  a  single  stamen  the  boxlike  part  at  the  end  is  the 
anther;  the  stalk  which  holds  the  anther  is  called  the  filaw,ent. 
The  anther  is  in  reality  a  hollow  box  which  produces  a  large 
number  of  little  grains  called  pollen.  Each  pistil  is  composed  of 
a  rather  stout  base  called  the  ovary,  and  a  more  or  less  lengthened 
portion  rising  from  the  ovary  called  the  style.  The  upper  end  of 
the  style,  which  in  some  cases  is  somewhat  broadened,  is  called  the 
stigma.  The  free  end  of  the  stigma  usually  secretes  a  sweet  fluid 
in  which  grains  of  pollen  from  flowers  of  the  same  kind  can  grow. 

Insects  as  Pollinating  Agents.  —  Insects  often  visit  flowers  to 
obtain  pollen  as  well  as  nectar.  In  so  doing  they  may  transfer 
some  of  the  pollen  from  one  flower  to  another  of  the  same  kind. 
This  transfer  of  pollen,  called  pollination,  is  of  the  greatest  use  to 
the  plant,  as  we  will  later  prove.  No  one  who  sees  a  hive  of  bees 
with  their  wonderful  communal  life  can  fail  to  see  that  these  insects 
play  a  great  part  in  the  life  of  the  flowers  near  the  hive.  A  famous 
observer  named  Sir  John  Lubbock  tested  bees  and  wasps  to  see 
how  many  trips  they  made  daily  from  their  homes  to  the  flowers, 
and  found  that  the  wasp  went  out  on  116  visits  during  a  working 
day  of  16  hours,  while  the  bee  made  but  a  few  less  visits,  and 
worked  only  a  little  less  time  than  the  wasp  worked.  It  is  evident 
that  in  the  course  of  so  many  trips  to  the  fields  a  bee  must  light  on 
hundreds  of  flowers. 

Adaptations  in  a  Bee.  —  If  we  look  closely  at  the  bee,  we  find  the 
body  and  legs  more  or  less  covered  with  tiny  hairs ;  especially  are 
these  hairs  found  on  the  legs.  When  a  plant  or  animal  structure 
is  fitted  to  do  a  certain  kind  of  work,  we  say  it  is  adapted  to  do  that 
work.  The  joints  in  the  leg  of  the  bee  adapt  it  for  complicated 
movements ;  the  arrangement  of  stiff  hairs  along  the  edge  of  a 
concavity  in  one  of  the  joints  of  the  leg  forms  a  structure  well 


INTERRELATIONS  OF  PLANTS  AND  ANIMALS     37 

adapted  to  hold  pollen.  In  this  way  pollen  is  collected  by  the  bee 
and  taken  to  the  hive  to  be  used  as  food.  But  while  gathering 
pollen  for  itself,  the  dust  is  caught  on  the  hairs  and  other  pro- 


Bumblebees,     a,  queen;  6,  worker;  c,  drone. 

jections  on  the  body  or  legs  and  is  thus  carried  from  flower  to 
flower.     The  value  of  this  to  a  flower  we  will  see  later. 

Field  Work.  —  Is  Color  or  Odor  in  a  Flower  an  Attraction  to  an  Insect? 
—  Sir  John  Lubbock  tried  an  experiment  which  it  would  pay  a  number  of 
careful  pupils  to  repeat.  He  placed  a  few  drops  of  honej^  on  glass  slips 
and  placed  them  over  papers  of  various  colors.  In  this  way  he  found  that 
the  honeybee,  for  example,  could  evidently  distinguish  different  colors. 
Bees  seemed  to  prefer  blue  to  any  other  color.  Flowers  of  a  yellow  or 
flesh  color  were  preferred  by  flies.  It  would  be  of  considerable  interest 
for  some  student  to  work  out  this  problem  with  our  native  bees  and  witli 
other  insects  by  using  paper  flowers  and  honey  or  sirup.  Test  the  keen- 
ness of  sight  in  insects  by  placing  a  white  object  (a  white  golf  ball  will  do) 
in  the  grass  and  see  how  many  insects  will  alight  on  it.  Try  to  work  out 
some  method  by  which  you  can  decide  whether  a  given  insect  is  attracted 
to  a  flower  by  odor  alone. 

The  Sight  of  the  Bumblebee.  —  The  large  eyes  located  on  the 
sides  of  the  head  are  made  up  of  a  large  number  of  little  units, 
each  of  which  is  considered  to  be  a  very  simple  eye.  The  large 
eyes  are  therefore  called  the  compound  eyes.  All  insects  are  pro- 
vided with  compound  eyes,  with  simple  eyes,  or  in  most  cases 
with  both.  The  simple  eyes  of  the  bee  may  be  found  by  a  careful 
observer  between  and  above  the  compound  eyes. 


38    INTERRELATIONS   OF   PLANTS   AND   ANIMALS 


Insects  can,  as  we  have  already  learned,  distinguish  differences 
in  color  at  some  distance ;   they  can  see  moving  objects,  but  they 

do  not  seem  to  be  able 
'  to  make  out  form  well. 

To  make  up  for  this, 
they  appear  to  have 
an  extremely  well- 
developed  sense  of 
smell.  Insects  can  dis- 
tinguish at  a  great  dis-' 
tance  odors  which  to  the 
human  nose  are  indis- 
tinguishable. Night- 
flying  insects,  espe- 
cially, find  the  flowers 
by  the  odor  rather 
than  by  color. 

Mouth  Parts  of  the 
Bee.  —  The  mouth  of 
the  bee  is  adapted  to 
take  in  the  foods  we 
have  mentioned,  and  is  used  for  the  purposes  for  which  man 
would  use  the  hands  and  fingers.  The  honeybee  laps  or  sucks 
nectar  from  flowers,  it  chews  the  pollen,  and  it  uses  part  of  the 
mouth  as  a  trowel  in  making  the  honeycomb.  The  uses  of  the 
mouth  parts  may  be  made  out  by  watching  a  bee  on  a  well-opened 
flower. 

Suggestions  for  Field  Work.  —  In  any  locality  where  flowers  are  abun- 
dant, try  to  answer  the  following  questions:  How  many  bees  visit  the 
locality  in  ten  minutes  ?  How  many  other  insects  alight  on  the  flowers  ? 
Do  bees  visit  flowers  of  the  same  kinds  in  succession,  or  fly  from  one 
flower  on  a  given  plant  to  another  on  a  plant  of  a  different  kind  ?  If  the 
bee  lights  on  a  flower  cluster,  does  it  visit  more  than  one  flower  in  the 
same  cluster?  How  does  a  bee  alight?  Exactly  what  does  the  bee  do 
when  it  alights? 

Butter  and  Eggs  (Linaria  vulgaris).  —  From  July  to  October 
this  very  abundant  weed  may  be  found  especially  along  roadsides 


The  head  of  a  bee.  A,  antennae  or  "feelers"; 
E,  compound  eye;  S,  simple  eye;  M,  mouth 
parts;  T,  tongue. 


INTERRELATIONS   OF  PLANTS   AND  ANIMALS    39 


and  in  sunny  fields.  The  flower  cluster 
forms  a  tall  and  conspicuous  cluster  of 
orange  and  yellow  flowers. 

The  corolla  projects  into  a  spur  on 
the  lower  side ;  an  upper  two-parted 
lip  shuts  down  upon  a  lower  three- 
parted  lip.  The  four  stamens  are  in 
pairs,  two  long  and  two  short. 

Certain  parts  of  the  corolla  are  more 
brightly  colored  than  the  rest  of  the 


Flower  cluster  of  "  butter  and 
eggs." 

flower.    This  color  is  a 
guide  to  insects.     But- 
ter and  eggs  is  visited 
most    by   bumblebees, 
which   are   guided    by 
the  orange  lip  to  alight 
just    where    they   can 
push    their    way    into 
the  flower.     The   bee, 
seeking  the  nectar  secreted  in  the  spur, 
brushes  its  head   and   shoulders  against 
the  stamens.     It  may  then,  as  it  pushes 
down  after  nectar,  leave  some  pollen  upon 
the  pistil,  thus  assisting  in  self-pollination. 
Visiting  another  flower  of  the  cluster,  it 
would  be  an  easy  matter  •  accidentally  to  transfer 


Diagram  to  show  how  the  bee  pollinates  "  butter  and  eggs." 
The  bumblebee,  upon  entering  the  flower,  rubs  its  head  against  the  long  pair  of 
anthers  (a),  then  continuing  to  press  into  the  flower  so  as  to  reach  the  nectar 
at  (A^)  it  brushes  against  the  stit-ima  (.S),  thus  pollinating  the  flower.  Inasmuch 
as  bees  visit  other  flowers  in  the  same  cluster,  cross-pollination  would  also  be 
likely.     Why? 


40    INTERRELATIONS  OF  PLANTS  AND  ANIMALS 


this  pollen  to  the  stigma  of  another  flower.  In  this  way  pollen 
is  carried  by  the  insect  to  another  flower  of  the  same  kind.  This 
is  known  as  cross-pollination.  By  pollination  we  mean  the  transfer 
of  pollen  from  an  a7ither  to  the  stigma  of  a  flower.  Self-pollination  is 
the  transfer  of  pollen  from  the  anther  to  the  stigma  of  the  same  flower; 
cross-pollination  is  the  transfer  of  pollen  from  the  anthers  of  one 
flower  to  the  stigma  of  another  flower  on  the  same  or  another  plant 
of  the  same  kind. 

History  of  the  Discoveries  regarding  Pollination  of  Flowers.  — 
Although  the  ancient  Greek  and  Roman  naturalists  had  some  vague 

ideas  on  the  subject  of  pollina- 
tion, it  was  not  until  the  first 
part  of  the  nineteenth  century 
that  a  book  appeared  in  which 
a  German  named  Conrad 
Sprengel  worked  out  the  facts 
that  the  structure  of  certain 
flowers  seemed  to  be  adapted 
to  the  visits  of  insects.  Cer- 
tain facilities  were  offered  to 
an  insect  in  the  way  of  easy 
foothold,  sweet  odor,  and 
especially  food  in  the  shape  of 
pollen  and  nectar,  the  latter  a 
sweet-tasting  substance  manu- 
factured by  certain  parts  of  the 
flower  known  as  the  neetar 
glands.  Sprengel  further  dis- 
covered the  fact  that  pollen 
could  be  and  was  carried  by 
the  insect  visitors  from  the 
anthers  of  the  flower  to  its 
stigma.  It  was  not  until  the  middle  of  the  nineteenth  century, 
however,  that  an  Englishman,  Charles  Darwin,  applied  Sprengel's 
discoveries  on  the  relation  of  insects  to  flowers  by  his  investiga- 
tions upon  cross-pollination.  The  growth  of  the  pollen  on  the 
stigma  of  the  flower  results  eventually  in  the  production  of  seeds. 


A  wild  orchid,  a  flower  of  the  typ3  from 
which  Charles  Darwin  worked  out  his 
theory  of  cross-pollination  by  insects. 


INTERRELATIONS   OF   PLANTS   AND   ANIMALS    41 

and  thus  new  plants.  Many  species  of  flowers  are  self-pollinated 
and  do  not  do  so  well  in  seed  production  if  cross-pollinated,  but 
Charles  Darwin  found  that  some  flowers  which  were  self-pollinated 
did  not  produce  so  many  seeds,  and  that  the  plants  which  grew  from 
their  seeds  were  smaller  and  weaker  than  plants  from  seeds  pro- 
duced by  cross-pollinated  flowers  of  the  same  kind.  He  also  found 
that  plants  grown  from  cross-pollinated  seeds  tended  to  vary  more 
than  those  grown  from  self-pollinated  seed.  This  has  an  important 
bearing,  as  we  shall  see  later,  in  the  production  of  new  varieties 
of  plants.  Microscopic  examination  of  the  stigma  at  the  time  of 
pollination  also  shows  that  the  pollen  from  another  flower  usually 
germinates  before  the  pollen  which  has  fallen  from  the  anthers  of 
the  same  flower.  This  latter  fact  alone  in  most  cases  renders  it 
unlikely  for  a  flower  to  produce  seeds  by  its  o^vn  pollen.  Darwin 
worked  for  years  on  the  pollination  of  many  insect-visited  flowers, 
and  discovered  in  almost  every  case  that  showy,  sweet-scented, 
or  otherwise  attractive  flowers  were  adapted  or  fitted  to  be  cross- 
pollinated  by  insects.  He  also  found  that,  in  the  case  of  flowers 
that  were  inconspicuous  in  appearance,  often  a  compensation 
appeared  in  the  odor  which  rendered  them  attractive  to  certain 
insects.  The  so-called  carrion  flowers,  pollinated  by  flies,  are 
examples,  the  odor  in  this  case  being  like  decayed  flesh.  Other 
flowers  open  at  night,  are  white,  and  provided  with  a  powerful 
scent.     Thus  they  attract  night-flying  moths  and  other  insects. 

Other  Examples  of  Mutual  Aid  between  Flowers  and  Insects.  — 
Many  other  examples  of  adaptations  to  secure  cross-pollination 
by  means  of  the  visits  of  insects  might  be  given.  The  mountain 
laurel,  which  makes  our  hillsides  so  beautiful  in  late  spring,  shows 
a  remarkable  adaptation  in  having  the  anthers  of  the  stamens 
caught  in  little  pockets  of  the  corolla.  The  weight  of  the  visiting 
insect  on  the  corolla  releases  the  anther  from  the  pocket  in  which 
it  rests  so  that  it  springs  up,  dusting  the  body  of  the  visitor  with 
pollen. 

In  some  flowers,  as  shown  by  the  primroses  or  primula  of  our 
hothouses,  the  stamens  and  pistils  are  of  different  lengths  in  different 
flowers.  Short  styles  and  long  or  high-placed  filaments  are  found 
in  one  flower,  and  long  styles  with  short  or  low-placed  filaments 


42    INTERRELATIONS   OF  PLANTS   AND  ANIMALS 


The  condition  of  stamens  and  pistils  on  the  spiked 
loosestrife  {Lythrum  salicaria). 


in  the  other.  Pollination  will  be  effected  only  when  some  of  the 
pollen  from  a  low-placed  anther  reaches  the  stigma  of  a  short- 
styled  flower,  or  when  the  pollen  from  a  high  anther  is  placed  upon 

a  long-styled  pistil. 
There  are,  as  in  the 
case  of  the  loosestrife, 
flowers  having  pistils 
and  stamens  of  thtee 
lengths.  Pollen  only 
grows  on  pistils  of  the 
same  length  as  the 
stamens  from  which  it 
came. 

The  milkweed  or 
butterfly  weed  already 
mentioned  is  another  example  of  a  flower  adapted  to  insect  pol- 
lination.^ 

A  very  remarkable  instance  of  insect  help  is  found  in  the  polli- 
nation of  the  yucca,  a  semitropical  lily 
which  lives  in  deserts  (to  be  seen  in 
most  botanic  gardens).  In  this  flower 
the  stigmatic  surface  is  above  the 
anther,  and  the  pollen  is  sticky  and 
cannot  be  transferred  except  by  insect 
aid.  This  is  accomplished  in  a  re- 
markable manner.  A  little  moth, 
called  the  pronuba,  after  gathering 
pollen  from  an  anther,  deposits  an  egg 
in  the  ovary  of  the  pistil,  and  then 
rubs  its  load  of  pollen  over  the  stigma 
of  the  flower.  The  young  hatch  out 
and  feed  on  the  young  seeds  which  have  grown  because  of  the 
pollen  placed  on  the  stigma  by  the  mother.     The  baby  cater- 


The  pronuba  moth  within  the 
yucca  flower. 


^  For  an  excellent  account  of  cross-pollination  of  this  flower,  the  reader  is  re- 
ferred to  W.  C.  Stevens,  Introduction  to  Botany.  Orchids  are  well  known  to  botan- 
ists as  showing  some  very  wonderful  adaptations.  A  classic  easily  read  is  Darwin, 
On  the  Fertilization  of  Orchids. 


INTERRELATIONS   OF   PLANTS   AND   ANIMALS    43 


pillars  eat  some  of  the  devel- 
oping seeds  and  later  bore 
out  of  the  seed  pod  and 
escape  to  the  ground,  leav- 
ing the  plant  to  develop 
the  remaining  seeds  without 
further  molestation. 

The  fig  insect  {Blastophaga 
grossorum)  is  another  mem- 
ber of  the  insect  tribe  that 
is  of  considerable  economic 
importance.  It  is  only  in  The  pronuba  polli- 
recent  years   that   the  fruit      "f^^^  *^^  p^*^ 

^  of  the  yucca. 

growers   of   California   have 
T,  ,    .  ,      .       discovered  that  the  fertilization  of  the  female 

Pod   of   yucca  showing 

where  the  young  pro-    flowcrs  is  brought  about  by  a  gallfly  which 

nubas  escaped.  bores   into  the  young  fruit.     By  importing 

the  gallflies  it  has  been  possible  to  grow  figs  where  for  many 
years  it  was  believed  that  the  climate  prevented  figs  from 
ripening. 

Other  Flower  Visitors.  —  Other  insects  besides  those  already 
mentioned  are  pollen  carriers  for  flowers.  Among  the  most  use- 
ful are  moths  and  butterflies.  Projecting  from  each  side  of  the 
head  of  a  butterfly  is  a  fluffy  structure,  the  palp.  This  collects 
and  carries  a  large  amount 
of  pollen,  which  is  deposited 
upon  the  stigmas  of  other 
flowers  when  the  butterfly 
pushes  its  head  down  into 
the  flower  tube  after  nectar. 
The  scales  and  hairs  on  the 
wings,  legs,  and  body  also 
carry  pollen. 

Flies  and  some  other  in- 
sects   are   agents    in    cross- 

pollination.     Humming  birds        ^  ^^^^^,,^  bird  about  to  cross-pollinate 

are    also    active    agents    in  a  lily. 


44    INTERRELATIONS  OF  PLANTS  AND   ANIMALS 

some  flowers.  Snails  are  said  in  rare  instances  to  carry  pollen. 
Man  and  the  domesticated  animals  undoubtedly  frequently 
pollinate  flowers  by  brushing  past  them  through  the  fields. 

Pollination  by  the  Wind.  —  Not  all  flowers  are  dependent  upon 
insects  or  other  animals  for  cross-pollination.  Many  of  the  earliest 
of  spring  flowers  appear  almost  before  the  insects  do.  Such  flowers 
are  dependent  upon  the  wind  for  carrying  pollen  from  the  stamens 


A  cornfield  showing  staminate  and  pistillate  flowers,  the  latter  having  becoms 
grains  of  corn.     An  ear  of  corn  is  a  bunch  of  ripened  fruits. 


of  one  flower  to  the  pistil  of  another.  Most  of  our  common  trees, 
oak,  poplar,  maple,  and  others,  are  cross-pollinated  almost  en- 
tirely by  the  wind. 

Flowers  pollinated  by  the  wind  are  generally  inconspicuous 
and  often  lack  a  corolla.  The  anthers  are  exposed  to  the  wind 
and  provided  with  much  pollen,  while  the  surface  of  the  stigma 
may  be  long  and  feathery.  Such  flowers  may  also  lack  odor,  nectar, 
and  bright  color.     Can  you  tell  why  ? 

Imperfect  Flowers.  —  Some  flowers,  the  wind-pollinated  ones 
in  particular,  are  imperfect ;    that  is,  they  lack  either  stamens 


INTERRELATIONS   OF  PLANTS  AND   ANIMALS    45 


or  pistils.  Again,  in  some  cases,  imperfect  flowers  having  stamens 
only  are  alone  found  on  one  plant,  while  those  flowers  having 
pistils  only  are  found  on  another  plant  of  the  same  kind.  '  In  such 
flowers,  cross-pollination  must  of  necessity  follow.  Many  of  our 
common  trees  are  examples. 

Other  Cases.  —  The  stamens  and  pistil  ripen  at  different  times 
in  some  flowers.     The  ''  Lady  Washington  "  geranium,  a  common 


The  flower  of  "  Lady  Washington  "  geranium,  in  which  stamens  and  pistil  ripen 
at  different  times,  thus  insuring  cross-polUnation.  A,  flower  with  ripe 
stamens;  B,  flower  with  stamens  withered  and  ripe  pistil. 

house  plant,  shows  this  condition.    Here  also  cross-pollination  must 
take  place  if  seeds  are  to  be  formed. 

Summary.  —  If  we  now  collect  our  observations  upon  flowers 
with  a  view  to  making  a  summary  of  the  different  devices  flowers 
have  assumed  to  prevent  self-pollination  and  to  secure  cross- 
pollination,  we  find  that  they  are  as  follows  :  — 

(1)  The  stamens  and  pistils  may  be  found  in  separate  flowers ^ 
either  on  the  same  or  on  different  plants. 

(2)  The  stamens  may  produce  pollen  before  the  pistil  is  ready  to 
receive  it,  or  vice  versa. 

(3)  The  stamens  and  pistils  may  be  so  placed  with  reference  to  each 
other  that  pollination  can  be  brought  about  only  by  outside  assistance. 


46    INTERRELATIONS   OF  PLANTS  AND  ANIMALS 

Artificial  Cross-pollination  and  its  Practical  Benefits  to  Man.  — 
Artificial  cross-pollination  is  practiced  by  plant  breeders  and  can 
easily  be  tried  in  the  laboratory  or  at  home.  First  the  anthers 
must  be  carefully  removed  from  the  bud  of  the  flower  so  as  to  elim- 
inate all  possibility  of  self-pollination.  The  flower  must  then  be 
covered  so  as  to  prevent  access  of  pollen  from  without ;  when  the 
ovary  is  sufficiently  developed,  pollen  from  another  flower,  having 
the  characters  desired,  is  placed  on  the  stigma  and  the  flower 
again  covered  to  prevent  any  other  pollen  reaching  the  flower. 
The  seeds  from  this  flower  when  planted  inay  give  rise  to  plants 
with  the  best  characters  of  each  of  the  plants  which  contributed 
to  the  making  of  the  seeds. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.    American  Book  Company. 
Andrews,  A  Practical  Course  in  Botany,  pages  214-249.    American  Book  Company. 
Atkinson,  First  Studies  of  Plant  Life,  Chaps.  XXV-XXVI.     Ginn  and  Company. 
Coulter,  Plant  Life  and  Plant  Uses,  pages  301-322.     American  Book  Company. 
Dana,  Plants  and  their  Children,  pages  187-255.     American  Book  Company. 
Lubbock,  Flowers,  Fruits,  and  Leaves,  Part  I.     The  Macmillan  Company. 
Needham,  General  Biology,  pages  1-50.     The  Comstock  Publishing  Company. 
Newell,  A  Reader  in  Botany,  Part  II,  pages  1-96.     Ginn  and  Company. 
Sharpe,  A  Laboratory  Manual  in  Biology,  pages  43-48.     American  Book  Company. 

ADVANCED 

BaUey,  Plant  Breeding.     The  Macmillan  Company. 

Campbell,  Lectures  on  the  Evolution  of  Plants.     The  Macmillan  Company. 

Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Part  II.  American  Book  Com- 
pany. 

Darwin,  Different  Forms  of  Floioers  on  Plants  of  the  Same  Species.  D.  Appleton 
and  Company. 

Darwin,  Fertilization  in  the  Vegetable  Kingdom,  Chaps.  I  and  II.  D.  Appleton 
and  Company. 

Darwin,  Orchids  Fertilized  by  Insects.     D.  Appleton  and  Company. 

Lubbock,  British  Wild  Flowers.     The  Macmillan  Company. 

Miiller,  The  Fertilization  of  Flowers.     The  Macmillan  Company. 


IV.   THE  FUNCTIONS  AND  COMPOSITION   OF  LIVING 

THINGS 

rroblems.  —  To  discover  the  functions  of  living  matter. 
(a)  In  a  living  plant, 
(6)  In  a  living  animal. 

Laboratory  Suggestions 

Laboratory  study  of  a  living  'plant.  —  Any  whole  plant  may  be  used  ;  a 
weed,  is  preferable. 

Laboratory  demonstration  or  home  study. — The  functions  of  a  living 
animal. 

Demonstration.  —  The  growth  of  pollen  tubes. 

Laboratory  exercise.  —  The  growth  of  the  matm'e  ovary  into  the  fruit, 
e.g.  bean  or  pea  pod. 

A  Living  Plant  and  a  Living  Animal  Compared.  —  A  walk  into 
the  fields  or  any  vacant  lot  on  a  day  in  the  early  fall  will  give  us 
first-hand  acquaintance  with  many  common  plants  which,  be- 
cause of  their  ability  to  grow  under  somewhat  unfavorable  condi- 
tions, are  called  weeds.  Such  plants  —  the  dandelion,  butter  and 
eggs,  the  shepherd's  purse  —  are  particularly  well  fitted  by  na- 
ture to  produce  many  of  their  kind,  and  by  this  means  drive  out 
other  plants  which  cannot  do  this  so  well.  On  these  or  other 
plants  we  find  feeding  several  kinds  of  animals,  usually  insects. 

If  we  attempt  to  compare,  for  example,  a  grasshopper  with  the 
plant  on  which  it  feeds,  we  see  several  points  of  likeness  and  dif- 
ference at  once.  Both  plant  and  insect  are  made  up  of  parts, 
each  of  which,  as  the  stem  of  the  plant  or  the  leg  of  the  insect, 
appears  to  be  distinct,  but  which  is  a  part  of  the  whole  living  plant 
or  animal.  Each  part  of  the  living  plant  or  animal  which  has  a 
separate   work   to  do   is    called    an    organ.       Thus   i)lants    and 

animals  are  spoken  of  as  living  organisms. 

47 


48 


FUNCTIONS  OF  LIVING  THINGS 


Functions  of  the  Parts  of  a  Plant.  —  We  are  all  familiar  with 
the  parts  of  a  plant,  —  the  root,  stem,  leaves,  flowers,  and  fruit. 
But  we  may  not  know  so  much  about  their  uses  to  the  plant.     Each 

of  these  structures  differs  from  every  other 
part,  and  each  has  a  separate  work  or  func- 
tion to  perform  for  the  plant.  The  root 
holds  the  plant  firmly  in  the  ground  and  takes 
in  water  and  mineral  matter  from  the  soil; 
the  stem  holds  the  leaves  up  to  the  light  and 
acts  as  a  pathway  for  fluids  between  the  root 
and  leaves;  the  leaves,  under  certain  condi- 
tions, manufacture  food  for  the  plant  and 
breathe;  the  flowers  form  the  fruits;  the  fruits 
hold  the  seeds,  which  in  turn  hold  young 
plants  which  are  capable  of  reproducing  adult 
plants  of  the  same  kind. 

The  Functions  of  an  Animal.  —  As  we 
have  already  seen,  the  grasshopper  has  a 
head,  a  jointed  body  composed  of  a  middle 
and  a  hind  part,  three  pairs  of  jointed  legs, 
and  two  pairs  of  wings.  Obviously,  the 
wings  and  legs  are  used  for  movement ;  a 
careful  watching  of  the  hind  part  of  the 
animal  shows  us  that  breathing  movements 
are  taking  place ;  a  bit  of  grass  placed  before  it  may  be  eaten, 
the  tiny  black  jaws  biting  little  pieces  out  of  the  grass.  If 
disturbed,  the  insect  hops  away,  and  if  we  try  to  get  it,  it  jumps 
or  flies  away,  evidently  seeing  us  before  we  can  grasp  it.  Hundreds 
of  little  grasshoppers  on  the  grass  indicate  that  the  grasshopper 
can  reproduce  its  own  kind,  but  in  other  respects  the  animal  seems 
quite  unlike  the  plant.  The  animal  moves,  breathes,  feeds,  and 
has  sensation,  while  apparently  the  plant  does  none  of  these.  It 
will  be  the  purpose  of  later  chapters  to  prove  that  the  functions 
of  plants  and  animals  are  in  many  respects  similar  and  that  both 
plants  and  animals  breathe,  feed,  and  reproduce. 

Organs.  —  If  we  look  carefully  at  the  organ  of  a  plant  called  a 
leaf,  we  find  that  the  materials  of  which  it  is  composed  do  not  ap- 


A  weed  —  notice  the  un- 
favorable environment. 


FUNCTIONS  OF  LIVING  THINGS 


49 


pear  to  be  everywhere  the  same. 
The  leaf  is  much  thinner  and 
more  delicate  in  some  parts 
than  in  others.  Holding  the 
flat,  expanded  blade  away  from 
the  branch  is  a  little  stalk, 
which  extends  into  the  blade  of 
the  leaf.  Here  it  splits  up  into 
a  network  of  tiny  "  veins  " 
which  evidently  form  a  frame- 
work for  the  flat  blade  some- 
what as  the  sticks  of  a  kite 
hold  the  paper  in  place.  If  we 
examine  under  the  compound 
microscope  a  thin  section  cut 
across  the  leaf,  we  shall  find 
that  the  veins  as  well  as  the 


Section  through  the  blade  of  a  leaf,  e, 
cells  of  the  upper  surface  ;  d,  cells  of  the 
lower  surface  ;  i,  air  spaces  in  the  leaf  ; 
V,  vein  in  cross  sections  ;  p,  green  cells. 


other  parts  are  made  up  of  many  tiny  boxlike  units  of  various 
sizes  and  shapes.     These  smallest  units  of  building  material  of  the 

plant  or  animal  disclosed  by  the 
compound  microscope  are  called 
cells.  The  organs  of  a  plant  or 
animal  are  built  of  these  tiny 
structures. 

Tissues.^  —  The  cells  which 
form  certain  parts  of  the  veins, 
the  flat  blade,  or  other  portions 
of  the  plant,  are  often  found  in 
groups  or  collections,  the  cells 
of  which  are  more  or  less  alike 


Several  cells  of  Elodea,  a  water  plant. 
chl.,  chlorophyll  bodies;  c.s.,  cell  sap; 
C.W.,  cell  wall ;  n.,  nucleus ;  p.  proto- 
plasm. The  arrows  show  the  direc- 
tion of  the  protoplasmic  movement. 


^  To  the  Teacher.  —  Any  simple  plant  or  animal  tissue  can  be  used  to  demon- 
strate the  cell.  Epidermal  cells  may  be  stripped  from  the  body  of  the  frog  or 
obtained  by  scraping  the  inside  of  one's  mouth.  The  thin  skin  from  an  onion 
stained  with  tincture  of  iodine  shows  well,  as  do  thin  sections  of  a  young  stem,  as 
the  bean  or  pea.  One  of  the  best  places  to  study  a  tissue  and  the  cells  of  which 
it  is  composed  is  in  the  leaf  of  a  green  water  plant,  Elodea.  In  this  plant  the  cells 
are  large,  and  not  only  their  outline,  but  the  movement  of  the  living  matter  within 
the  cells,  may  easily  be  seen,  and  the  parts  described  in  the  next  paragraph  ca." 
be  demonstrated. 

HUNTER,   CIV.   BI. — 4 


50  FUNCTIONS   OF   LIVING   THINGS 

in  size  and  shape.  Such  a  collection  of  cells  is  called  a  tissue. 
Examples  of  tissues  are  the  cells  covering  the  outside  of  the  human 
body,  the  muscle  cells,  which  collectively  allow  of  movement,  bony 
tissues  which  form  the  framework  to  which  the  muscles  are  at- 
tached, and  many  others. 

Cells.  —  A  cell  may  be  defined  as  a  tiny  mass  of  living  matter 
containing   a   nucleus,  either    living   alone   or  forming    a  unit  of 

the  building  material  of  a  living  thing.  The 
living  matter  of  which  all  cells  are  formed  is 
known  as  protoplasrro  (formed  from  two  Greek 
words  meaning  first  form).  If  we  examine 
under  a  compound  microscope  a  small  bit  of 
the  water  plant  Elodea,  we  see  a  number  of 
structures  resembling  bricks  in  a  wall.  Each 
"  brick,"    however,    is    really   a    plant    cell 


-CltA. 


iT'V:.-v.  ■  •  "(iv-  :•;  ••••':K 
ivX'afe-"  .■•-■••.':■;  •.■':'.-'V-.J 


A  ceu.     ch.,   chromo-   bounded  by  a  thin  Wall.      If  we  look  carefully, 

somes;  c.«\,  celJ  wall ;  "^  ...  . 

n.,  nucleus ;  p.,  proto-   we  Can  See  that  the  material  inside  of  this  wall 
^  ^^'  is  slowly  moving  and  is  carrying  around  in  its 

substance  a  number  of  little  green  bodies.  This  moving  substance 
is  living  matter,  the  protoplasm  of  the  cell.  The  green  bodies 
(the  chlorophyll  bodies)  we  shall  learn  more  about  later ;  they  are 
found  only  in  plant  cells.  All  plant  and  animal  cells  appear 
to  be  alike  in  the  fact  that  every  living  cell  possesses  a  structure 
known  as  the  nucleus  (pi.  nuclei),  which  is  found  within  the  body 
of  the  cell.  This  nucleus  is  not  easy  to  find  in  the  cells  of  Elodea. 
Within  the  nucleus  of  all  cells  are  found  certain  bodies  called 
chromosomes.  These  chromosomes  in  a  given  plant  or  animal  are 
always  constant  in  number.  These  chromosomes  are  supposed  to 
be  the  bearers  of  the  qualities  which  we  believe  can  be  handed 
down  from  plant  to  plant  and  from  animal  to  animal,  in  other 
words,  the  inheritable  qualities  which  make  the  offspring  like  its 
parents. 

How  Cells  form  Others.  —  Cells  grow  to  a  certain  size  and  then 
split  into  two  new  cells.  In  this  process,  which  is  of  very  great 
importance  in  the  growth  of  both  plants  and  animals,  the  nucleus 
divides  first.  The  chromosomes  also  divide,  each  splitting  length- 
wise and  the  parts  going  in  equal  numbers  to  each  of  the  two  cells 


FUNCTIONS  OF  LIVING   THINGS 


51 


Stages  in  the  division  of  one  cell  to  form  two. 
Which  part  of  the  cell  diAddes  first  ?  What  seems 
to  become  of  the  chromosomes  ? 


formed  from  the  old  cell.  In  this  way  the  matter  in  the  chromosomes 
is  divided  equally  between  the  two  new  cells.  Then  the  rest  of 
the  protoplasm  separates,  and  two  new  cells  are  formed.  This 
process  is  known  as  fis- 
sion. It  is  the  usual 
method  of  growth  found 
in  the  tissues  of  plants 
and  animals. 

Cells  of  Various  Sizes 
and  Shapes.  —  Plant 
cells  and  animal  cells  are 
of  very  diverse  shapes 
and  sizes.  There  are 
cells  so  large  that  they 
can  easily  be  seen  with 
the  unaided  eye ;  for 
example,  the  root  hairs 
of  plants  and  eggs  of  some  animals.  On  the  other  hand,  cells 
may  be  so  minute,  as  in  the  case  of  the  plant  cells  named  bacteria, 
that  several  million  might  be  present  in  a  few  drops  of  milk.  The 
forms  of  cells  may  be  extremely  varied  in  different  tissues ;  they 
may  assume  the  form  of  cubes,  columns,  spheres,  flat  plates,  or 
may  be  extremely  irregular  in  shape.  One  kind  of  tissue  cell, 
found  in  man,  has  a  body  so  small  as  to  be  quite  invisible  to  the 
naked  eye,  although  it  has  a  prolongation  several  feet  in  length. 
Such  are  some  of  the  cells  of  the  nervous  system  of  man  and  other 
large  animals,  as  the  ox,  elephant,  and  whale. 

Varying  Sizes  of  Living  Things.  —  Plant  cells  and  animal  cells 
may  live  alone,  or  they  may  form  collections  of  cells.  Some 
plants  are  so  simple  in  structure  as  to  be  formed  of  only  one  kind 
of  fcells.  Usually  living  organisms  are  composed  of  several  groups 
of  different  kinds  of  cells.  It  is  only  necessary  to  call  attention 
to  the  fact  that  such  collections  of  cells  may  form  organisms  so 
tiny  as  to  be  barely  visible  to  the  eye ;  as,  for  instance,  some  of  the 
small  flowerless  plants  or  many  of  the  tiny  animals  living  in  fresli 
water  or  salt  water.  On  the  other  hand,  among  animals,  the  bulk 
of  the  elephant  and  whale,  and  among  plants  the  big  trees  of  Cali- 


52  FUNCTIONS   OF   LIVING   THINGS 

fornia,  stand  out  as  notable  examples.     The  large  plants  and  ani- 
mals are  made  up  of  more,  not  necessarily  larger,  cells. 

What  Protoplasm  can  Do.  —  It  responds  to  influences  or  stimu- 
lation from  without  its  own  substance.  Both  plants  and  animals 
are  sensitive  to  touch  or  stimulation  by  light,  heat  or  coid,  certain 
chemical  substances,  gravity,  and  electricity.  Green  plants  turn 
toward  the  source  of  light.  Some  animals  are  attracted  to  light 
and  others  repelled  by  it;  the  earthworm  is  an  example  of  the 
latter.     Protoplasm  is  thus  said  to  be  irritable. 

Protoplasrn  has  the  power  to  contract  and  to  move.  Muscular 
movement  is  a  familiar  instance  of  this  power.  Movement 
may  also  take  place  in  plants.  Some  plants  fold  up  their  leaves 
at  night ;  others,  like  the  sensitive  plant,  fold  their  leaflets  when 
touched. 

Protoplasm  can  form  new  limng  matter  out  of  food.  To  do  this, 
food  materials  must  be  absorbed  into  the  cells  of  the  living 
organism.  To  make  protoplasm,  it  is  evident  that  the  same  chem- 
ical elements  must  enter  into  the  composition  of  the  food  sub- 
stances as  are  found  in  living  matter.  The  simplest  plants  and 
animals  have  this  wonderful  power  as  certainly  developed  as  the 
most  complex  forms  of  life. 

Protoplasm,  be  it  in  plant  or  animal,  breathes  and  throws  off  waste 
materials.  When  a  living  thing  does  work  oxygen  unites  with  food 
in  the  body ;  the  food  is  burned  or  oxidized  and  work  is  done  by 
means  of  the  energy  released  from  the  food.  The  waste  materials 
are  excreted  or  passed  out.  Plants  and  animals  alike  pass  off  the 
carbon  dioxide  which  results  from  the  oxidation  of  food  and  of 
parts  of  their  own  bodies.  Animals  eliminate  wastes  containing 
nitrogen  through  the  skin  and  the  kidneys. 

Protoplasm  can  reproduce,  that  is,  form  other  matter  like  itself. 
New  plants  are  constantly  appearing  to  take  the  places  of  those 
that  die.  The  supply  of  living  things  upon  the  earth  is  not  de- 
creasing; reproduction  is  constantly  taking  place.  In  a  general 
way  it  is  possible  to  say  that  plants  and  animals  reproduce  in  a 
very  similar  manner. 

The  Importance  of  Reproduction.  —  Reproduction  is  the  final 
process  that  plants  and   animals  are   called  upon  to  perform. 


FUNCTIONS  OF  LIVING  THINGS 


53 


Without  the  formation  of  new  living  things  no  progress  would  be 
possible  on  the  earth.  We  have  found  that  insects  help  flowering 
plants  in  this  process.  Let  us  now  see  exactly  what  happens 
when  pollen  is  placed  by  the  bee  on  the  stigma  of  another  flower 
of  the  same  kind.  To  understand  this  process  of  reproduction  in 
flowers,  we  must  first  study  carefully  pollen  grains  from  the  anther 
of  some  growing  flower. 

Pollen.  —  Pollen  grains  of  various  flowers,  when  seen  under  the 
microscope,  differ  greatly  in  form  and  appearance.  Some  are  rela- 
tively large,  some  small,  some  rough,  others  smooth,  some  spherical, 


Pollen  grains  of  different  shapes  and  sizes. 

and  others  angular.  They  all  agree,  however,  in  having  a  thick 
wall,  with  a  thin  membrane  under  it,  the  whole  inclosing  a  mass 
of  protoplasm.  At  an  early  stage  the  pollen  grain  contains  but  a 
single  cell.  A  little  later,  however,  two  nuclei  may  be  found  in  the 
protoplasm.  Hence  we  know  that  at  least  two  cells  exist  there,  one 
of  which  is  called  the  sperm  cell ;  its  nucleus  is  the  sperm  nucleus. 
Growth  of  Pollen  Grains.  —  Under  certain  conditions  a  i)ollen 
grain  will  grow  or  germinate.  This 
growth  can  be  artificially  produced  in 
the  laboratory  by  sprinkling  pollen 
from  well-opened  flowers  of  sweet  pea 
or  nasturtium  on  a  solution  of  L5 
parts  of  sugar  to  100  of  water.  Left 
for  a  few  hours  in  a  warm  and  moist 
place  and  then  examined  under  the 
microscope,  the  grains  of  pollen  will 
be  found  to  have  germinated,  a  long, 
threadlike  mass  of  protoplasm  grow- 
ing from  it  into  the  sugar  solution. 


A  pollen  grain  greatly  magnified. 
Two  nuclei  are  found  {n,  n)  at 
this  stage  of  its  growth. 


FUNCTIONS  OF  LIVING  THINGS 


The  presence  of  this  sugar 
solution  was  sufficient  to 
induce  growth.  When  the 
pollen  grain  germinates, 
the  nuclei  enter  the  thread- 
like growth  (this  growth  is 
called  the  pollen  tube ;  see 
Figure) .  One  of  the  nuclei 
which  grows  into  the  pollen 
tube  is  known  as  the  syenn 

Three  stages  in  the  germination  of  the  pollen  UUCieus. 

grain.     The  nuclei  in  the  tube  in  (3)   are  Fertilization    of    the 
the  sperm  nuclei.     Drawn  under  the  com- 
pound microscope.  Flower.  —  It    we    cut    the 

pistil  of  a  large  flower  (as  a 
lily)  lengthwise,  we  notice  that  the  style  appears  to  be  composed 
of  rather  spongy  material  in  the  in- 
terior; the  ovary  is  hollow  and  is 
seen  to  contain  a  number  of  rounded 
structures  which  appear  to  grow  out 
from  the  wall  of  the  ovary.  These 
are  the  ovules.  The  ovules,  under 
certain  conditions,  will  become  seeds. 
An  explanation  of  these  conditions 
may  be  had  if  we  examine,  under 
the  microscope,  a  very  thin  section 
of  a  pistil,  on  which  pollen  has  be- 
gun to  germinate.  The  central  part 
of  the  style  is  found  to  be  either 
hollow  or  composed  of  a  soft  tissue 
through  which  the  pollen  tube  can 
easily    grow.      Upon    germination, 

the    pollen    tube     grows     downward      Fertilization  of  the  ovule.     A  flower 
,  ,     ^  cut  down  lengthwise   (only  one 

through  the  spongy  center  of  the       side  shown).    The  pollen  tube  is 

style,  follows  the  path  of  least  resist-  ^f^""  entering  the  ovule,     a,  an- 

.      ,  1  . , ,  .      , ,  ther ;  /,  filament ;  pg,  pollen  gram; 

ance  to  the  space  Wlthm  the  ovary,  s,  stigmatic    surface ;   pt,   poUen 

and   there   enters   the   ovule.        It   is  tube  ;  sf,  style  ;  o,  ovary  ;  m,  micro- 

.      .    .    ^  pyle;    sp,   space    withm    ovary; 

believed  that  some  chemical  influ-       e,  egg  cell ;  P,  petal ;  s,  sepal. 


FUNCTIONS  OF  LIVING  THINGS 


55 


ence  thus  attracts  the  pollen  tube.  When  it  reaches  the  ovaiy, 
the  sperm  cell  penetrates  an  ovule  by  making  its  way  through  a 
little  hole  called  the  micropyle.  It  then  grows  toward  a  clear 
bit  of  protoplasm  known  as  the  embryo  sac.  The  embryo  sac  is 
an  ovoid  space,  microscopic  in  size,  filled  with  semifluid  protoplasm 
containing  several  nuclei.  (See  Figure.)  One  of  the  nuclei,  with 
the  protoplasm  immediately  surrounding  it,  is  called  the  egg  cell.  It 
is  this  cell  that  the  sperm  nucleus  of  the  pollen  tube  grows  to- 
ward ;  ultimately  the  sperm  nucleus  reaches  the  egg  nucleus  and 
unites  with  it.  The  two  nuclei,  after  coming  together,  unite  to  form 
a  single  cell.  This  process  is  known  as  fertilization.  This  single 
cell  formed  by  the  union  of  the  pollen  tube  cell  or  sperm  and  the 
egg  cell  is  now  called  a  fertilized  egg. 

Development  of  Ovule  into  Seed.  —  The  primary  reason  for 
the  existence  of  a  flower  is  that  it  may  produce  seeds  from  which  future 
plants  will  grow.  After  fertilization  the  ovide  grows  into  a  seed. 
The  first  beginning  of  the  growth  of  the  seed  takes  place  at  the 
moment  of  fertilization.  From  that  time  on  there  is  a  growth 
of  the  fertilized  egg  within  the  ovule  which  makes  a  baby  plant 
called  the  embryo.     The  embryo  will  give  rise  to  the  adult  plant. 

A  Typical  Fruit,  —  the  Pea  or  Bean  Pod.  — 
If  a  withered  flower  of  any  one  of  the  pea  or 
bean  family  is  examined  carefully,  it  will  be 
found  that  the  pistil  of  the  flower  continues  to 
grow  after  the  rest  of  the  flower  withers.  If 
we  remove  the  pistil  from  such  a  flower  and 
examine  it  carefully,  we  find  that  it  is  the 
ovary  that  has  enlarged.  The  space  within 
the  ovary  has  become  nearly  filled  with  a 
number  of  nearly  ovoid  bodies,  attached 
along  one  edge  of  the  inner  wall.  These  we 
recognize  as  the  young  seeds. 

The  pod  of  a  bean,  pea,  or  locust  illustrates 
well  the  growth  from  the  flower.  The  pod, 
which  is  in  reality  a  ripened  ovary  with  other 
parts  of  the  pistil  attached  to  it,  is  considered 
as  a  fruit.     By  definition,  a  fruit  is  a  ripened 


s  — 


The  fruit  of  the  locust, 
a  bean-like  fruit. 
p,  the  attachment 
to  the  placenta ;  s, 
the  stigma. 


56 


FUNCTIONS  OF  LIVING  THINGS 


ovary  and  its  contents  together  with  any  parts  of  the  flower  that  may 
he  attached  to  it.  The  chief  use  of  the  fruit  to  the  flower  is  to 
hold  and  to  protect  the  seeds ;  it  may  ultimately  distribute  them 
where  they  can  reproduce  young  plants. 

The  Necessity  of  Fruit  and  Seed  Dispersal  to  a  Plant.  —  We 
have  seen  that  the  chief  reason  for  flowers,  from  the  plant's  stand- 
point, is  to  produce  fruits  which  contain  seeds.  Reproduction 
and  the  ultimate  scattering  of  fruits  and  seeds  are  absolutely  neces- 


The  development  of  an  apple.  Notice  that  in  this  fruit  additional  parts  besides 
the  ovary  (o)  become  part  of  the  fruit.  Certain  outer  parts  of  the  flower,  the 
sepals  (s)  and  receptacle,  become  the  fleshy  part  of  the  fruit,  while  the  ovary 
becomes  the  core.     Stages  numbered  1  to  7  are  in  the  order  of  development. 

sary  in  order  that  colonies  of  plants  may  reach  new  localities.  It 
is  evident  that  plants  best  fitted  to  scatter  their  seeds,  or  place 
fruits  containing  the  seeds  some  little  distance  from  the  parent 
plants,  are  the  ones  which  will  spread  most  rapidly.  A  plant,  if 
it  is  to  advance  into  new  territory,  must  get  its  seeds  there  first. 
Plants  which  are  best  fitted  to  do  this  are  the  most  widely  dis- 
tributed on  the  earth. 

How  Seeds  and  Fruits  are  Scattered.  —  Seed  dispersal  is  accom- 
plished in  many  different  ways.  Some  plants  produce  enormous 
numbers  of  seeds  which  may  or  may  not  have  special  devices  to 
9,id  in  their  scattering.    Most  weeds  are  thus  started  "  in  pastures 


FUNCTIONS  OF  LIVING  THINGS  57 

new."  Some  prolific  plants,  like  the  milkweed,  have  seeds  with  a 
little  tuft  of  hairlike  down  which  allows  them  to  be  carried  by  the 
wind.  Others,  as  the  omnipresent  dandelion,  have  their  fruits 
provided  with  a  similar  structure,  the  pappus.  Some  plants,  as 
the  burdock  and  clotbur,  have  fruits  provided  with  tiny  hooks 
which  stick  to  the  hair  of  animals,  thus  proving  a  means  of  trans- 
portation. Most  fleshy  fruits  contain  indigestible  seeds,  so  that 
when  the  fruits  are  eaten  by  animals  the  seeds  are  passed  off  from 
the  body  unharmed  and  may,  if  favorably  placed,  grow.  Nuts  of 
various  kinds  are  often  carried  off  by  animals,  buried,  and  for- 
gotten, to  grow  later.  Such  are  a  few  of  the  ways  in  which  seeds 
are  scattered.  All  other  things  being  equal,  the  plants  best 
equipped  to  scatter  seeds  or  fruits  are  those  which  will  drive  out 
other  plants  in  a  given  locality.  Because  of  their  adaptations 
they  are  likely  to  be  very  numerous,  and  when  unfavorable  con- 
ditions come,  for  that  reason,  If  for  no  other,  are  likely  to  survive. 
Such  plants  are  best  exemplified  in  the  weeds  of  the  grassplots 
and  gardens. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Andrews,  A  Practical  Course  in  Botany,  pages  250-270.     American  Book  Company. 
Atkinson,  First  Studies  of  Plant  Life,  Chaps.  XXV-XXVI.     Ginn  and  Company. 
Bailey,  Lessons  with  Plants,  Part  III,  pages  131-250.     The  Macmillan  Company. 
Coulter,  Plant  Life  and  Plant  Uses.     American  Book  Company. 
Dana,  Plants  and  their  Children,  pages  187-255.     American  Book  Company. 
Lubbock,  Flowers,  Fruit,  and  Leaves,  Part  I.     The  Macmillan  Company, 
Newell,  A  Reader  in  Botany,  Part  II,  pages  1-96.     Ginn  and  Company. 

ADVANCED 

Bailey,  Plant  Breeding.     The  Macmillan  Company. 

Campbell,  Lectures  on  the  Evolution  of  Plants.     The  Macmillan  Company. 

Coulter,  Barnes,  and  Cowles,  A   Textbook  of  Botany,  Part  II.     American  Book 

Company. 
Darwin,  Different  Forms  of  Flowers  on  Plants  of  the  Same  Species.     Appleton. 
Darwin,  Fertilization  in  the  Vegetable  Kingdom,  Chaps.  I  and  II.     Appleton. 
Darwin,  Orchids  Fertilized  by  Insects.     D.  Appleton  and  Company. 
Miiller,  The  Fertilization  of  Flowers.     The  Macmillan  Company. 


V.   PLANT    GROWTH    AND    NUTRITION.     CAUSES    OF 

GROWTH 

Problem.  —  What  causes  a  young  jjlant  to  grow  ? 
(a).  The  relation  of  the  young  plant  to  its  food  supply, 
ih)   The  outside  conditions  ivecessary  for  germination. 

(c)  What  the  young  plant  does  with  its  food  supply. 

(d)  How  a  plant  or  animal  is  able  to  use  its  food  supply. 

(e)  How  a  plant  or  aniinal  prepare  food  to  use  in  various 
parts  of  the  body. 

Laboratory  Suggestions 

Laboratory  exercise.  —  Examination  of  bean  in  pod.  Examination  and 
identification  of  parts  of  bean  seed. 

Laboratory  demonstration.  —  Tests  for  the  nutrients  :  starch,  fats  or 
oils,  protein. 

Laboratory  demonstration.  —  Proof  that  such  foods  exist  in  bean. 

Home  work.  —  Test  of  various  common  foods  for  nutrients.  Tabulate 
results. 

Extra  home  work  by  selected  pupils.  —  Factors  necessary  for  germina- 
tion of  bean.     Demonstration  of  experiments  to  class. 

Demonstration.  —  Oxidation  of  candle  in  closed  jar.  Test  with  lime 
water  for  products  of  oxidation. 

Demonstration.  —  Proof  that  materials  are  oxidized  within  the  human 
body. 

Demonstration.  —  Oxidation  takes  place  in  growing  seeds.  Test  for 
oxidation   products.     Oxygen   necessary   for   germination. 

Laboratory  exercise.  —  Examination  of  corn  on  cob,  the  corn  grain, 
longitudinal  sections  of  corn  grain  stained  with  iodine  to  show  that  embryo 
is  distinct  from  food  supply. 

Demonstration.  —  Test  for  grape  sugar. 

Demonstration.  —  Grape  sugar  present  in  growing  corn  grain. 

Demonstration.  —  The  action  of  diastase  on  starch.  Conditions  neces- 
sary for  action  of  diastase. 

What  makes  a  Seed  Grow.  —  The  general  problem  of  the  pages 
that  follow  will  be  to  explain  how  the  baby  plant,  or  embryo, 

5S 


PLANT  GROWTH   AND   NUTllITION 


59 


formed  in  the  seed  as  the  result  of  the  fertilization  of  the  egg  cell, 
is  able  to  grow  into  an  adult  plant.  Two  sets  of  factors  are  neces- 
sary for  its  growth :  first,  the  presence  of  food  to  give  the  young 
plant  a  start ;  second,  certain  stimulating  factors  outside  the  young 
plant,  such  as  water  and  heat. 

If  we  open  a  bean  pod,  we  find  the  seeds  lying  along  one  edge  of 
the  pod,  each  attached  by  a  little  stalk  to  the  inner  wall  of  the 
ovary.  If  we  pull  a  single  bean  from  its  attachment,  we  find  that 
the  stalk  leaves  a  scar  on  the 
coat  of  the  bean ;  this  scar  is 
called  the  hilum.  The  tirfy 
hole  near  the  hilum  is  called 
the  micropyle.  Turn  back  to 
the  figure  (page  54)  showing 
the  ovule  in  the  ovary.  Find 
there  the  little  hole  through 
which  the  pollen  tube  reached 
the  embryo  sac.  This  hole  is 
identical  with  the  micropyle 
in  the  seed.  The  thick  outer 
coat  (the  testa)  is  easily  re- 
moved from  a  soaked  bean, 
the  delicate  coat  under  it 
easily  escaping  notice.  The 
seed  separates  into  two  parts ; 
these  are  called  the  cotyledons. 
If  you  pull  apart  the  coty- 
ledons very  carefully,  you  find  certain  other  structures  between 
them.  The  rodlike  part  is  called  the  hypocotyl  (meaning  under 
the  cotyledons).  This  will  later  form  the  root  (and  part  of  the 
stem)  of  the  young  bean  plant.  The  first  true  leaves,  very  tiny 
structures,  are  folded  together  between  the  cotyledons.  That 
part  of  the  plant  above  the  cotyledons  is  known  as  the  plumule 
or  epicotyl  (meaning  above  the  cotyledons).  All  the  parts  of  the 
seed  within  the  seed  coats  together  form  the  embryo  or  young 
plant.  A  bean  seed  contains,  then,  a  tiny  plant  protected  by  a 
tough  coat. 


Three  views  of  a  kidney  bean,  the  lower 
one  having  one  cotyledon  removed  to 
show  the  hypocotyl  and  plumule. 


60  PLANT   GROWTH   AND  NUTRITION 

Food  in  the  Cotyledons.  —  The  problem  now  before  us  is  to  find 
out  how  the  embryo  of  the  bean  is  adapted  to  grow  into  an  adult 
plant.  Up  to  this  stage  of  its  existence  it  has  had  the  advantage 
of  food  and  protection  from  the  parent  plant.  Now  it  must  begin 
the  battle  of  life  alone.  We  shall  find  in  all  our  work  with  plants 
and  animals  that  the  problem  of  food  supply  is  always  the  most 
important  problem  to  be  solved  by  the  growing  organism.  Let 
us  see  if  the  embryo  is  able  to  get  a  start  in  life  (which  many 
animals  get  in  the  egg)  from  food  provided  for  it  within  its  own 
body. 

Organic  Nutrients.  —  Organic  foods  (those  which  come  from 
living  sources)  are  made  up  of  two  kinds  of  substances,  the  nutri- 
ents or  food  substances  and  wastes  or  refuse.  An  egg,  for  example, 
contains  the  white  and  the  yolk,  composed  of  nutrients,  and  the 
shell,  which  is  waste.  The  organic  nutrients  are  classed  in  three 
groups. 

Carbohydrates,  foods  which  contain  carbon,  hydrogen,  and 
oxygen  in  a  certain  fixed  proportion  (CeHioOs  is  an  example). 
They  are  the  simplest  of  these  very  complex  chemical  compounds 

we  call  organic  nutrients.     Starch  and  sugar 
are  common  examples  of  carbohydrates. 

Fats  and  Oils.  —  These  foods  are  also  com- 
posed of  carbon,  hydrogen,  and  oxygen  in  a 
proportion  which  enables  them  to  unite 
readily  with  oxygen. 

Proteins.  —  A  third  group  of  organic  foods, 
Starcii  grains  in  the  cells    proteins,   are  the  most   complex  of   all   in 

of  a  potato  tuber.  ,  i     •  • ,  •  i  i  i       •  i  i 

their  composition,  and  have,  besides  carbon, 
oxygen,  and  hydrogen,  the  element  nitrogen  and  minute  quantities 
of  other  elements. 

Test  for  Starch.  —  If  we  boil  water  with  a  piece  of  laundry  starch 
in  a  test  tube,  then  cool  it  and  add  to  the  mixture  two  or  three 
drops  of  iodine  solution,^  we  find  that  the  mixture  in  the  test  tube 

1  Iodine  solution  is  made  by  simply  adding  a  few  crystals  of  the  element  iodine 
to  95  per  cent  alcohol ;  or,  better,  take  by  weight  1  gram  of  iodine  crystals,  f  gram 
of  iodide  of  potassium,  and  dilute  to  a  dark  brown  color  in  weak 'alcohol  (35  per 
cent)  or  distilled  water. 


PLANT   GROWTH   AND  NUTRITION 


61 


Test  for  starch. 


turns  purple  or  deep  blue.     It  has  been  discovered  by  experiment 

that  starch,  and  no  other  known  substance,  will  be  turned  purple  or 

dark  blue  by  iodine.     Therefore,  iodine 

solution  has  come  to  be  used  as  a  test 

for  the  presence  of  starch. 

Starch  in  the  Bean.  —  If  we  mash 

up  a  little  piece  of  a  bean  cotyledon 

which  has  been  previously  soaked  in 

water,  and  test  for  starch  with  iodine 

solution,  the  characteristic  blue-black 

color  appears,  showing  the  presence  of 

the  starch.     If  a  little  of  the  stained 

material  is  mounted  in  water  on  a  glass 

slide  under  the  compound  microscope, 

you  will  find  that  the  starch  is  in  the 

form  of  little  ovoid  bodies  called  starch  grains.     The  starch  grains 

and  other  food  products  are  made  use  of  by  the  growing  plant. 

Test  for  Oils.  —  If  the  substance 
believed  to  contain  oil  is  rubbed  on 
brown  paper  or  is  placed  on  paper  and 
then  heated  in  an  oven,  the  presence 
of  oil  will  be  known  by  a  translucent 
spot  on  the  paper. 

Protein  in  the  Bean.  —  Another 
nutrient  present  in  the  bean  cotyledon 
is  protein.  Several  tests  are  used  to 
detect  the  presence  of  this  nutrient. 
The  following  is  one  of  the  best 
known :  — 

Place  in  a  test  tube  the  substance 
to  be  tested ;  for  example,  a  bit  of 
hard-boiled  egg.  Pour  over  it  a  little 
strong  (60  per  cent)  nitric  acid  and  heat 
gently.     Note  the  color  that  appears 

—  a  lemon  yellow.     If  the  egg  is  washed  in  water  and  a  little 

ammonium  hydrate  added,  the  color  changes  to  a  deep  orange, 

showing  that  a  protein  is  present. 


V^         V^ 


Test  for  protein. 


62 


PLANT   GROWTH   AND   NUTRITION 


If  the  protein  is  in  a  liquid  state,  its  presence  may  be  proT^ed 
by  heating,  for  when  it  coagulates  or  thickens,  as  does  the  white 
of  an  egg  when  boiled,  protein  in  the  form  of  an  albumin  is  present. 

Another  characteristic  protein  test  easily  made  at  home  is 
burning  the  substance.  If  it  burns  with  the  odor  of  burning  feath- 
ers or  leather,  then  protein  forms  part  of  its  composition.^ 

A  test  of  the  cotyledon  of  a  bean  for  protein  food  with  nitric 
acid  and  ammonium  hydrate  shows  us  the  presence  of  this  food. 
Beans  are  found  by  actual  test  to  contain  about  23  per  cent  of 
protein,  59  per  cent  of  carbohydrates,  and  about  2  per  cent  oils. 
The  young  plant  within  a  pea  or  bean  is  thus  shown  to  be  well 
supplied  with  nourishment  until  it  is  able  to  take  care  of  itself. 
In  this  respect  it  is  somewhat  like  a  young  animal  within  the  egg, 
a  bird  or  fish,  for  example. 

Beans  and  Peas  as  Food  for  Man.  —  So  much  food  is  stored  in 
legumes  (as  beans  and  peas)  that  man  has  come  to  consider  them 
a  very  valuable  and  cheap  source  of  food.  Study  carefully  the 
following  table :  — 

Nutrients  furnished  for  Ten   Cents   in  Beans  and  Peas  at 

Certain  Prices  per  Pound 


Food  Materials  as  Purchased 


Kidney  beans,  dried 

Lima  beans,  fresh,  shelled  .     .     . 

Lima  beans,  dried 

String  beans,  fresh,  30  cents  per 

peck 

Beans,  baked,  canned  .  .  .  . 

Lentils,  dried 

Peas,  green,  in  pod,  30  cents  per 

peck 

Peas,  dried 


Prices 

PER 

Pound 


Cents 

5 

8 
6 

3 

5 

10 

3 
4 


Ten  Cents  will  pay-  fob  — 


Total 

Food 

Material 


Pounds 

2.00 
1.25 
1.67 

3.33 
2.00 
1.00 

3.33 
2.50 


Proteid 


Pounds 

0.45 
.04 
.30 

.07 
.14 
.26 

.12 
.62 


Fat 


Pounds 

0.04 

.03 

.01 
.05 
.01 

.01 
.03 


Carbo- 
hydrates 


Pounds 

1.19 

.12 

1.10 

.23 
.39 
.59 

.33 
1.55 


1  Other  tests  somewhat  more  reliable,  but  much  more  delicate,  are  the  biuret 
test  and  test  with  Millon's  reagent. 


PLANT   GROWTH   AND   NUTRITION 


63 


Germination  of  the  Bean.  —  If  dry  seeds  are  planted  in  sawdust 
or  earth,  they  will  not  grow.     A  moderate  supply  of  water  must  be 


A  series  of  early  stages  in  the  germination  of  the  kidney  bean. 

given  to  them.     If  seeds  were  to  be  kept  in  a  freezing  tempera- 
ture or  at  a  very  high  temperature,  no  growth  would  take  place. 
A  moderate   temperature  and 
a  moderate  water  supply  are 
most   favorable    for   their   de- 
velopment. 

If  some  beans  were  planted 
so  that  we  might  make  a  record 
of  their  growth,  we  would  find 
the  first  signs  of  germination 
to  be  the  breaking  of  the  testa 
and  the  pushing  outward  of 
the  hypocotyl  to  form  the  first 
root.  A  little  later  the  hypo- 
cotyl begins  to  curve  down- 
ward. A  later  stage  shows 
the  hypocotyl  lifting  the  coty- 
ledon upward.  In  consequence 
the  hypocotyl  forms  an  arch, 
dragging    after    it    the    bulky 

.    1     ^  mi  J.  Bean  seedlings.     The  older  seedlings  at 

cotyledons.       The     stem,     as       ^^^  ^^^^  ^^^^  ^sed  up  all  of  the  food 
soon  as  it  is  released  from  the       supply  in  the  cotyledons. 


64 


PLANT   GROWTH   AND   NUTRITION 


ground,  straightens  out.  From  between  the  cotyledons  the  bud- 
hke  plumule  or  epicotyl  grows  upward,  forming  the  first  true 
leaves  and  all  of  the  stem  above  the  cotyledons.  As  growth  con- 
tinues, we  notice  that  the  cotyledons  become  smaller  and  smaller, 
until  their  food  contents  are  completely  absorbed  into  the  young 
plant.  The  young  plant  is  now  able  to  care  for  itself  and  may 
be  said  to  have  passed  through  the  stages  of  germination. 

What  makes  an  Engine  Go.  —  If  we  examine  the  sawdust  or 
soil  in  which  the  seeds  are  growing,  we  find  it  forced  up  by  the 
growing  seed.  Evidently  work  was  done;  in  other  words,  energy 
was  released  by  the  seeds.  A  familiar  example  of  release  of 
energy  is  seen  in  an  engine.  Coal  is  placed  in  the  firebox  and 
lighted,  the  lower  door  of  the  furnace  is  then  opened  so  as  to  make 
a  draft  of  air  which  will  reach  the  coal.  You  know  the  result. 
The  coal  burns,  heat  is  given  off,  causing  the  water  in  the  boiler 

to  make  steam,  the  engine  wheels  to  turn, 
and  work  to  be  done.  Let  us  see  what 
happens  from  the  chemical  standpoint. 

Coal,  Organic  Matter.  —  Coal  is  made 
largely  from  dead  plants,  long  since  pressed 
into  its  present  hard  form.  It  contains  a 
large  amount  of  a  chemical  element  called 
carbon,  the  presence  of  which  is  character- 
istic of  all  organic  material. 

Oxidation,  its  Results.  —  When  things  con- 
taining carbon  are  lighted,  they  burn.  If  we 
place  a  lighted  candle  which  contains  carbon 
in  a  closed  glass  jar,  the  candle  soon  goes  out. 

The  limewater  test.  The  ^\  ^e  then  Carefully  test  the  air  in  the  jar 
tube  at  the  right  shows  with  a  substance  known  as  limewater,^  the 
dioxide.^  °      ^  ^^^  °^  latter,  when  shaken  up  with  the  air  in  the 

jar,  turns  milky.  This  test  proves  the  pres- 
ence in  the  jar  of  a  gas,  known  as  carbon  dioxide.  This  gas  is 
formed  by  the  carbon  of  the  candle  uniting  with  the  oxygen  in 

1  Limewater  can  be  made  by  shaking  up  a  piece  of  quicklime  the  size  of  your 
fist  in  about  two  quarts  of  water.  Filter  or  strain  the  limewater  into  bottles  and 
it  is  ready  for  use. 


PLANT  GROWTH  AND  NUTRITION 


65 


Diagram  to  show  that  when  a  piece  of 
wood  is  burned  it  forms  water  and 
carbon  dioxide. 


the  air.  When  the  oxygen  of  the  air  in  the  jar  was  used  up, 
the  flame  went  out,  showing  that  oxygen  is  necessary  to  make  a 
thing  burn.  This  uniting  of 
oxygen  with  some  other  sub- 
stance is  called  oxidation. 

Oxidation  possible  without  a 
Flame.  —  But  a  flame  is  not 
necessary  for  oxidation.  Iron, 
if  left  in  a  damp  place,  becomes 
rusty.  A  union  between  the 
oxygen  in  the  water  or  air  and 
the  iron  makes  what  is  known 
as  iron  oxide  or  rust.  This  is 
an  example  of  slow  oxidation. 

Oxidation  in  our  Bodies.  —  If  we  expel  the  air  from  our  lungs 
through  a  tube  into  a  bottle  of  limewater,  we  notice  the  lime- 
water  becomes  milky.  Evidently  carbon  dioxide  is  formed  in  our 
own  bodies  and  oxidation  takes  place  there.  Is  it  fair  to  believe 
that  the  heat  of  our  body  (for  example,  98.6°  Fahrenheit  under  the 
tongue)  is  due  to  oxidation  within  the  body,  and  that  the  work 
we  do  results  from  this  chemical  process.     If  so,  what  is  oxidized? 

Energy  comes  from  Foods.  —  From  the  foregoing  experiment 
it  is  evident  that  food  is  oxidized  within  the  human  body  to  re- 
lease energy  for  our  daily  work.  Is  it  not  logical  to  suppose  that 
all  living  things,  both  plant  and  animal,  release  energy  as  the  re- 
sult of  oxidation  of  foods  within  their  cells  ?  Let  us  see  if  this  is 
true  in  the  case  of  the  pea. 

Food  oxidized  in  Germinating  Seeds.  —  If  we  take  equal 
numbers  of  soaked  peas,  placed  in  two  bottles,  one  tightly  stop- 
pered, the  other  having  no  stopper,  both  bottles  being  exposed  to 
identical  conditions  of  light,  temperature,  and  moisture,  we  find 
that  the  seeds  in  both  bottles  start  to  germinate,  but  that  those 
in  the  closed  bottle  soon  stop,  while  those  in  the  open  jar  continue 
to  grow  almost  as  well  as  similar  seeds  placed  in  an  open  dish  would. 

Why  did  not  the  seeds  in  the  covered  jar  germinate?  To 
answer  this  question,  let  us  carefully  remove  the  stopper  from  the 
stoppered  jar  and  insert  a  lighted  candle.     The  candle  goes  out 

HUNTER,    CIV.    BI. 5 


66 


PLANT  GROWTH  AND   NUTRITION 


at  once.     The  surer  test  of  limewater  shows  the  presence  of  car- 
bon dioxide  in  the  jar.     The  carbon  of  the  foodstuffs  of  the  pea 

united  with  the  oxygen 
of  the  air,  forming  car- 
])on  dioxide.  Growth 
stopped  as  soon  as  the 
oxygen  was  exhausted. 
The  presence  of  carbon 
dioxide  in  the  jar  is  an 
indication  that  a  very 
important  process  which 
we  associate  with  animals 
rather  than  plants,  that 
of  respiration,  is  taking 
place.  The  seed,  in  order 
to  release  the  energy 
locked  up  in  its  food 
supply,  must  have  oxy- 
gen, so  that  the  oxida- 
tion of  the  food  may  take 
place.  Hence  a  constant  supply  of  fresh  air  is  an  important  factor 
in  germination.  It  is  important  that  air  should  penetrate  between 
the  grains  of  soil  around  a  seed.  The  frequent  stirring  of  the  soil 
enables  the  air  to  reach  the  seed.  Air  also  acts 
upon  some  materials  in  the  soil  and  puts  them 
in  a  form  that  the  germinating  seed  can  use. 
This  necessity  for  oxygen  shows  us  at  least 
one  reason  why  the  farmer  plows  and  harrows 
a  field  and  one  important  use  of  the  earthworm. 
Explain. 

Structure  of  a  Grain  of  Corn.  —  Examination 
of  a  well-soaked  grain  of  corn  discloses  a  difference 
in  the  two  flat  sides  of  the  grain.  A  light-colored 
area  found  on  one  surface  marks  the  position  of 
the  embryo;  the  rest  of  the  grain  contains  the 
food  supply.  The  interesting  thing  to  remember  here  is  that  the 
food  supply  is  outside  of  the  embryo. 


Experiment  that  shows  the  necessity  for  air  in 
germination. 


grain  of  corn 
cut  lengthwise. 
C,  cotyledon; 
E,  endosperm; 
H,  hypocotyl; 
P,  plumule. 


PLANT  GROWTH  AND  NUTRITION 


67 


A  grain  cut  lengthwise  perpendicular  to  the  flat  side  and  then 
dipped  in  weak  iodine  shows  two  distinct  parts,  an  area  containing 
considerable  starch,  the  endosperm,  and  the  embryo  or  young 
plant.  Careful  inspection  shows  the  hypo- 
cotyl  and  plumule  (the  latter  pointing  toward 
the  free  end  of  the  grain)  and  a  part  surround- 
ing them,  the  single  cotyledon  (see  Figure). 
Here  again  we  have  an  example  of  a  fitting 
for  future  needs,  for  in  this  fruit  the  one  seed 
has  at  hand  all  the  food  material  necessary 
for  rapid  growth,  although  the  food  is  here 
outside  the  embryo. 

Endosperm  the  Food  Supply  of  Corn.  — 
We  find  that  the  one  cotyledon  of  the  corn 
grain  does  not  serve  the  same  purpose  to 
the  young  plant  as  do  the  two  cotyledons  of 
the  bean.  Although  we  find  a  little  starch 
in  the  corn  cotyledon,  still  it  is  evident  from 
our  tests  that  the  endosperm  is  the  chief  source 
of  food  supply.  The  study  of  a  thin  section 
of  the  corn  grain  under  the  compound  micro- 
scope shows  us  that  the  starch  grains  in  the 
endosperm  are  large  and  regular  in  size. 
When  the  grain  has  begun  to  grow,  examina- 
tion shows  that  the  starch  grains  near  the 
edge  of  the  cotyledon  are  much  smaller  and 
quite  irregular,  having  large  holes  in  them. 
We  know  that  the  germinating  grain  has  a 
much  sweeter  taste  than  that  which  is  not  Longitudinal  section  of 
growing.  This  is  noticed  in  sprouting  barley  young  ear  of  corn, 
or  malt.  We  shall  later  find  that,  in  order 
to  make  use  of  starchy  food,  a  plant  or  animal 
must  in  some  manner  change  it  over  to  sugar. 
This  change  is  necessary,  because  starch  will 
not  dissolve  in  water,  while  sugar  will ;  in  this  form  substances 
can  pass  from  cell  to  cell  in  the  plant  and  thus  distribute  the  food 
where  it  is  needed. 


stigmas :  SH,  the 
sheath-like  leaves : 
ST,  the  flower  stalk. 
(After  Sargent.) 


68 


PLANT  GROWTH  AND  NUTRITION 


+ 

Test  for  grape  sugar. 


A  Test  for  Grape  Sugar.  —  Place  in  a  test  tube  the  substance  to 
be  tested  and  heat  it  in  a  little  water  so  as  to  dissolve  the  sugar. 

Add  to  the  fluid  twice  its  bulk  of 
Fehling's  solution/  which  has  been 
previously  prepared.  Heat  the  mix- 
ture, which  should  now  have  a  blue 
color,  in  the  test  tube.  If  grape  sugar 
is  present  in  considerable  quantity,  the 
contents  of  the  tube  will  turn  first  a 
greenish,  then  yellow,  and  finally  a 
brick-red  color.  Smaller  amounts  will 
show  less  decided  red.  No  other  sub- 
stance than  sugar  will  give  this  reac- 
tion. If  Benedict's  test  ^  is  used,  a 
colored  precipitate  will  appear  in  the 
test  tube  after  boiling. 

Starch  changed  to  Grape  Sugar  in 
the  Corn.  —  That  starch  is  being 
changed  to  grape  sugar  in  the  germi- 
nating corn  grain  can  easily  be  shown  if  we  cut  lengthwise  through 
the  embryos  of  half  a  dozen  grains  of  corn  that  have  just  begun 
to  germinate,  place  them  in  a  test  tube  with  some  Fehling's  solu- 
tion, and  heat  almost  to  the  boiling  point.  They  will  be  found 
to  give  a  reaction  showing  the  presence  of  sugar  along  the  edge 
of  the  cotyledon  and  between  it  and  the  endosperm. 

Digestion.  —  This  change  of  starch  to  grape  sugar  in  the  corn 
is  a  process  of  digestion.  If  you  chew  a  bit  of  unsweetened  cracker 
in  the  mouth  for  a  little  time,  it  will  begin  to  taste  sweet,  and  if 
the  chewed  cracker,  which  we  know  contains  starch,  is  tested 
with  Fehling's  solution,  some  of  the  starch  will  be  found  to  have 
changed  to  grape  sugar.  Here,  again,  a  process  of  digestion  has 
taken  place.  In  both  the  corn  and  in  the  mouth,  the  change  is 
brought  about  by  the  action  of  peculiar  substances  known  as 
digestive  ferments,  or  enzymes.  Such  substances  have  the  power 
under  certain  conditions  to  change  insoluble  foods  —  solids  —  into 

1  Directions  for  making  these  solutions  will  be  found  in  Hunter's  Laboratory 
Problems  in  Civic  Biology. 


PLANT  GROWTH  AND  NUTRITION 


69 


soluble  substances  —liquids.     The  result  is  that  substances  which 
before  digestion  would  not  dissolve  in  water  now  will  dissolve. 

The  Action  of  Diastase  on  Starch.  —  The  enzyme  found  in  the 
cotyledon  of  the  corn,  which  changes  starch  to  grape  sugar,  is 
called  diastase.  It  may  be  separated  from 
the  cotyledon  and  used  in  the  form  of  a 
powder. 

To  a  little  starch  in  half  a  cup  of  water 
we  add  a  very  little  (1  gram)  of  diastase 
and  put  the  vessel  containing  the  mixture 
in  a  warm  place,  where  the  temperature 
will  remain  nearly  constant  at  about  98° 
Fahrenheit.  On  testing  part  of  the  con- 
tents at  the  end  of  half  an  hour,  and  the 
remainder  the  next  morning,  for  starch  and 
for  grape  sugar,  we  find  from  the  morning 
test  that  the  starch  has  been  almost  com- 
pletely changed  to  grape  sugar.  Starch 
and  warm  water  alone  under  similar  con- 
ditions will  not  react  to  the  test  for  grape 
sugar. 

Digestion  has  the  Same  Purpose  in  Plants 
and  Animals.  —  In  our  own  bodies  we 
know  that  solid  foods  taken  into  the  mouth  are  broken  up  by  the 
teeth  and  moistened  by  saliva.  If  we  could  follow  that  food,  we 
would  find  that  eventually  it  became  part  of  the  blood.  It  was 
-made  soluble  by  digestion,  and  in  a  liquid  form  was  able  to  reach 
the  blood.  Once  a  part  of  the  body,  the  food  is  used  either  to 
release  energy  or  to  build  up  the  body. 

Summary.  —  We  have  seen  : 

1.  That  seeds,  in  order  to  grow,  must  possess  a  food  supply 
either   in  or  around  their  bodies. 

2.  That  this  food  supply  must  be  oxidized  before  energy  is 
released. 

3.  That  in  cases  where  the  food  is  not  stored  at  the  point 
where  it  is  to  be  oxidized  the  food  must  be  digested  so  that  it 
may  be  transported  from  one  part  to  another  in  the  same  plant. 


A  germinating  corn  grain. 
C,  cotyledon;  H,  grow- 
ing root  (hypocotyl);  P, 
growing  stem  (plumule)  ; 
S,  endosperm;  d.s.,  di- 
gested starch;  p.r.,  pri- 
mary root;  s.r.,  second- 
ary root;  r.h.,  root  hairs. 


70  PLANT  GROWTH  AND  NUTRITION 

The  life  processes  of  plants  and  animals,  so  far,  may  be  con- 
sidered as  alike;  they  both  feed,  breathe  (oxidize  their  food),  do 
work,  and  grow. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Andrews,  A  Practical  Course  in  Botany,  pages  1-21.     American  Book  Company. 

Atkinson,  First  Studies  of  Plant  Life,  Chap.  XXX.     Ginn  and  Company. 

Bailey,  Botany,  Chaps.  XX,  XXX.     The  Macmillan  Company. 

Beal,  Seed  Dispersal.     Ginn  and  Company. 

Bergen  and  Davis,  Principles  of  Botany,  Chaps.  XX,  XXX.     Ginn  and  Company. 

Coulter,  Plant  Life  and  Plant  Uses.     American  Book  Company. 

Dana,  Plants  and  their  Children,.     American  Book  Company. 

Mayne  and  Hatch,  High  School  Agriculture.     American  Book  Company. 

Lubbock,  Flowers,  Fruits,  and  Leaves.     The  Macmillan  Company. 

Newell,  Reader  in  Botany,  pages  24-49.     Ginn  and  Company. 

Sharpe,  A  Laboratory  Manual  in  Biology,  pages  55-65.    American  Book  Company 


ADVANCED 

Bailey,  The  Evolution  of  our  Native  Fruits.     The  Macmillan  Company. 

Bailey,  Plant  Breeding.     The  Macmillan  Company. 

Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Vol.  I.     American  Book  Com 
pany. 

De  CandoUe,  Origin  of  Cultivated  Plants.     D.  Appleton  and  Company. 

Duggar,  Plant  Physiology.     The  Macmillan  Company. 

Farmers'  Bulletins,  Nos.  78,  86,  225,  344.     U.  S.  Department  of  Agriculture. 

Hodge,  Nature  Study  and  Life,  Chaps.  X,  XX.     Ginn  and  Company. 

Kerner  (translated  by  Oliver),  Natural  History  of  Plants.      Henry  Holt  and  Com- 
pany,    4  vols.     Vol.  II,  Part  2. 

Sargent,  Corn  Plants.     Houghton,  Mifflin,  and  Company. 


VI.     THE  ORGANS  OF  NUTRITION  IN  PLANTS  — THE 
SOIL  AND  ITS  RELATION  TO  THE  ROOTS 

Problem.  —  What  (i  plant  takes  froin  the  soil  and  how  it  gets 
it. 

{a)  What  determines  the  direction  of  growth  of  roots  ? 

(h)  Hoiv  is  the  root  built  ? 

(c)  How  does  a  root  absorh  water  ? 

id)  What  is  in  tl%e  soil  that  a  root  might  tahe  owt  ? 

{e)  Why  is  nitrogen  necessary,  and  how  is  it  obtained  ? 

Laboratory  Suggestions 

Demonstration.  —  Roots  of  bean  or  pea. 

Demonstration  or  home  experiment.  —  Response  of  root  to  gfravity  and  to 
water.     What  part  of  root  is  most  responsive  ? 

Laboratory  work.  —  Root  hairs,  radish  or  corn,  position  on  root,  gross 
structure  only.     Drawing. 

Demonstration.  —  Root  hair  under  compound  microscope. 

Demonstration.  —  Apparatus  illustrating  osmosis. 

Demonstration  or  a  home  experiment.  —  Organic  matter  present  in  soil. 

Demonstration.  —  Root  tubercles  of  legume. 

Demonstration.  —  Nutrients  present  in  some  roots. 

Uses  of  the  Root.  —  If  one  of  the  seedlings  of  the  bean  spoken  of 
in  the  last  chapter  is  allowed  to  grow  in  sawdust  and  is  given 
light,  air,  and  water,  sooner  or  later  it  will  die.  Soil  is  part  of 
its  natural  environment,  and  the  roots  which  come  in  contact  ^\^th 
the  soil  are  very  important.  It  is  the  purpose  of  this  chapter  to 
find  out  just  how  the  young  plant  is  fitted  to  get  what  it  needs 
from  this  part  of  its  environment ;  namely,  the  soil. 

The  development  of  a  bean  seedling  has  sho^vn  us  that  the  root 
grows  first.  One  of  the  most  important  functions  of  the  root  to  a  young 
seed  plant  is  that  of  a  holdfast,  an  anchor  to  fasten  it  in  the  place  ichere 
it  is  to  develop.  It  has  many  other  uses,  as  the  taking  in  of  water 
with  the  mineral  and  organic  matter  dissolved  therein,  the  stor- 

71 


72 


SOIL  AND  ITS  RELATION  TO  ROOTS 


A  root  system,  showing  primary 
and  secondary  roots. 


age  of  food,  climbing,  etc.  All 
functions  other  than  the  first  one 
stated  arise  after  the  young  plant 
has  begun  to  develop. 

Root  System.  —  If  you  dig  up  a 
young  bean  seedling  and  carefully 
wash  the  dirt  from  the  roots,  you 
will  see  that  a  long  root  is  devel- 
oped as  a  continuation  of  the  hy- 
pocotyl.  This  root  is  called  the 
primary  root.  Other  smaller  roots 
which  grow  from  the  primary  root 
are  called  secondary,  or  tertiary, 
depending  on  their  relation  to  the 
first  root  developed. 

Downward  Growth  of  Root. 
Influence   of    Gravity.  —  Most   of 

the  roots  examined  take  a  more  or  less  downward  direction.     We 

are  all  familiar  with  the  fact  that  the  force  we  call  gravity  influences 

life  upon  this  earth  to  a  great  degree.     Does  gravity  act  on  the 

growing  root?     This  question  may  be 

answered  by  a  simple  experiment. 
Plant  mustard  or  radish  seeds  in  a 

pocket  garden,  place  it  on  one  edge 

and  allow  the  seeds  to  germinate  until 

the  root  has  grown  to  a  length  of  about 

half  an  inch.      Then  turn  it  at  right 

angles  to  the  first  position  and  allow  it 

to  remain    for    one    day   undisturbed. 

The  roots  now  will  be  found  to  have 

turned  in  response  to  the  change  in 

position,   that  part  of  the  root   near 

the    growing    point   being    the    most 

sensitive    to    the    change.      This    ex- 
periment seems   to    indicate    that    the       Revolve  this  figure  in  the  direc- 

roots  are  influenced  to  grow  downward        *!^"^^  ^^  *^^^  arrows  t^  see  if 

^  the  roots   of  the   radish   re- 

by  the  force  of  gravity.  spond  to  gravity. 


^^^^^^^^^^^^^^^^^^^^^r  k-  ^^^^^B 

■  < 

m 

SOIL   AND   ITS   RELATION   TO   ROOTS  73 

Experiments  to  determine  the  Influence  of  Moisture  on  a  Grow- 
'ing  Root.  —  The  objection  might  well  be  interposed  that  possibly 
the  roots  in  the  pocket  garden  ^  grew  downward  after  water.  That 
moisture  has  an  influence  on  the  growing  root  is  easily  proved. 

Plant  bird  seed,  mustard  or  radish  seed  in  the  underside  of  a 
sponge,  which  should  be  kept  wet,  and  may  be  suspended  by  a 
string  under  a  bell  jar  in  the  schoolroom  window.  Note  whether 
the  roots  leave  the  sponge  to  grow  downward,  or  if  the  moisture 
in  the  sponge  is  sufficient  to  'counterbalance  the  force  of  gravity. 

Water  a  Factor  which  determines  the  Course  taken  by  Roots.  — 
Water,  as  well  as  the  force  of  gravity,  has  much  to  do  with  the  direction 
taken  by  roots.  Water  is  always  found  below  the  surface  of  the 
ground,  but  sometimes  at  a  great  depth.  Most  trees,  and  all 
grasses,  have  a  greater  area  of  surface  exposed  by  the  roots  than 
by  the  branches.  The  roots  of  alfalfa,  a  cloverlike  plant  used  for 
hay  in  the  Western  states,  often  penetrate  the  soil  after  water  for 
a  distance  of  ten  to  twenty  feet  below  the  surface  of  the  ground. 

Fine  Structure  of  a  Root.-  —  When  we  examine  a  delicate  root 
in  thin  longitudinal  section  under  the  compound  microscope, 
we  find  the  entire  root  to  be  made  up  of  cells,  the  walls  of  which 
are  uniformly  rather  thin.  Over  the  lower  end  of  the  root  is 
found  a  collection  of  cells,  most  of  which  are  dead,  loosely  arranged 
so  as  to  form  a  cap  over  the  growing  tip.  This  is  evidently  an 
adaptation  which  protects  the  young  and  actively  growing  cells 
just  under  the  root  cap.  In  the  body  of  the  root  a  central  cylinder 
can  easily  be  distinguished  from  the  surrounding  cells.  In  a 
longitudinal  section  a  series  of  tubelike  structures  may  be  found 
within  the  central  cylinder.  These  structures  are  cells  which  have 
grown  together  at  the  small  end,  the  long  axis  of  the  cells  running 

1  The  Pocket  Garden.  —  A  very  convenient  form  of  pocket  germinator  may  be 
made  as  follows.  Obtain  two  cleaned  four  by  five  negatives  (window  glass  will 
do)  ;  place  one  flat  on  the  table  and  place  on  this  half  a  dozen  pieces  of  colored 
blotting  paper  cut  to  a  size  a  little  less  than  the  glass.  Now  cnt  four  thin  strips  of 
wood  to  fit  on  the  glass  just  outside  of  the  paper.  Next  moisten  th(^  blotter,  place 
on  it  some  well-soaked  radish,  nmstard  seeds  or  barley  grains,  and  cover  with  the 
other  glass.  The  whole  box  thus  made  should  be  l)ound  together  with  bicycle  tape. 
Seeds  will  germinate  in  this  box  and  with  care  may  live  for  two  weeks  or  more. 

2  Sections  of  tradescantia  roots  are  excellent  for  demonstration  of  these  structures. 


74 


SOIL   AND   ITS   RELATION  TO   ROOTS 


Cross  section  of  a  young  taproot; 
a,  a,  root  hairs ;  b,  outer  layer  of 
bark;  c,  inner  layer  of  bark; 
d,  wood  or  central  cylinder. 


the  length  of  the  main  root.     In  their  development  the  cells  men- 
tioned have  grown  together  in  such  a  manner  as  to  lose  their  small 

ends,  and  now  form  continuous 
hollow  tubes  with  rather  strong 
walls.  Other  cells  have  come  to 
develop  greatly  thickened  walls ; 
these  cells  give  mechanical  sup- 
port to  the  tubelike  cells.  Col- 
lections of  such  tubes  and  sup- 
13orting  woody  cells  together  make 
up  what  are  known  as  fihrovascular 
bundles. 

Root  Hairs.  —  Careful  examina- 
tion of  the  root  of  one  of  the  seed- 
lings of  mustard,  radish,  or  barley 
grown  in  the  pocket  germinator 
shows  a  covering  of  tiny  fuzzy 
structures.  These  structures  are  very  minute,  at  most  3  to  4  milli- 
meters in  length.  They  vary  in  length 
according  to  their  position  on  the  root, 
the  most  and  the  longest  root  hairs 
being  found  near  the  point  marked 
R.  H.  in  the  figure.  These  structures 
are  outgrowths  of  the  outer  layer  of  the 
root  (the  epidermis),  and  are  of  very 
great  importance  to  the  living  plant. 

Structure  of  a  Root  Hair.  —  A  single 
root  hair  examined  under  a  compound 
microscope  will  be  found  to  be  a  long, 
round  structure,  almost  colorless  in  ap- 
pearance. The  wall,  which  is  very  flexi- 
ble and  thin,  is  made  up  of  cellulose,  a 
substance  somewhat  like  wood  in  chemi- 
cal composition,  through  which  fluids 
may  easily  pass.  Clinging  close  to  the 
cell  wall  is  the  protoplasm  of  the  cell. 
The  interior  of  the  root  hair  is  more  or  less  filled  with  a  fluid 


Young  embryo  of  corn,  show- 
ing root  hairs  (R.  H.)  and 
growing  stem  (P.)- 


SOIL   AND   ITS   RELATION  TO   ROOTS 


75 


Diagram  of  a  root  hair;  CS,  cell  sap;  CW,  cell 
wall ;  P,  protoplasm  ;  A^,  nucleus  ;  S,  particles 
of  soil. 


called  cell  sap.     Forming  a  part  of  the  living  protoplasm  of  the 

root  hair,  sometimes  in  the  hairlike  prolongation  and  sometimes 

in  that  part  of  the  cell  which  forms   the  epidermis,  is  found  a 

nucleus.     The  protoplasm  and   nucleus   are   alive ;  the  cell  wall 

formed  by  the  living  matter  in  the  cell  is  dead.     The  root  hair  is  a 

living  plant  cell  with  a  wall 

so  delicate  that  water  and 

mineral   substances  from 

the  soil  can  pass  through 

it  into  the  interior  of  the 

root. 

How  the  Root  absorbs 
Water.  —  The  process  by 
which  the  root  hair  takes 
up  soil  water  can  better 
be  understood  if  we  make 
an  artificial  root  hair  large  enough  to  be  easily  seen.  An  egg  with 
part  of  the  outer  shell  removed  so  as  to  expose  the  soft  skinlike 
membrane  underneath  is  an  example.  Better,  an  artificial  root 
hair  may  be  fnade  in  the  following  way.  Pour  some  soft  celloidin 
into  a  test  tube ;  carefully  revolve  the  test  tube  so  that  an  even 
film  of  celloidin  dries  on  the  inside.  This  membrane  is  removed, 
filled  with  white  of  egg,  and  tied  over  the  end  of  a  rubber  cork  in 
which  a  glass  tube  has  previously  been  inserted.  When  placed 
in  water,  it  gives  a  very  accurate  picture  of  the  root  hair  at 
work.  After  a  short  time  water  begins  to  rise  in  the  tube,  having 
passed  through  the  film  of  celloidin.  If  grape  sugar,  salt,  or  some 
other  substance  which  will  dissolve  in  water  were  placed  in  the 
water  outside  the  artificial  root  hair,  it  could  soon  be  proved  by 
test  to  pass  through  the  wall  and  into  the  liquid  inside. 

Osmosis.  —  To  explain  this  process  we  must  remember  that 
gases  and  liquids  of  different  densities,  when  separated  by  a  mem- 
brane, tend  to  flow  toward  each  other  and  mingle,  the  greater  flow 
always  being  in  the  direction  of  the  denser  medium.  The  process 
hy  which  two  gases  or  fluids,  separated  by  a  membrane,  tend  to  pass 
through  the  membrane  and  mingle  with  each  other,  is  called  osmosis. 
The  method  by  which  the  root  hairs  take  up  soil  water  is  exactly 


7G 


SOIL  AND   ITS   RELATION  TO   ROOTS 


the  same  process.  It  is  by  osmosis.  The  white  of  the  egg  is  the 
best  possible  substitute  for  Uviiig  matter ;  the  celloidin  membrane 
separating  the  egg  from  the  water  is  much  hke  the  dehcate  mem- 
brane-hke  wall  which  separates  the  protoplasm  of  the  root  hair 
from  the  water  in  the,  soil  surrounding  it.  The  fluid  in  the  root 
hair  is  denser  than  the  soil  water ;  hence  the  greater  flow  is  toward 
the  interior  of  the  root  hair.^ 

Passage  of  Soil  Water  within  the  Root.  — -  We  have  already  seen 
that  in  an  exchange  of  fluids  by  osmosis  the  greater  flow  is  always 
toward  the  denser  fluid.  Thus  it  is  that  the  root  hairs  take  in 
more  fluid  than  they  give  up.  The  cell  sap,  which  partly  fills 
the  interior  of  the  root  hair,  is  a  fluid  of  greater  density  than  the 
water  outside  in  the  soil.     When  the  root  hairs  become  filled  with 


The  soil  particles  are  each  surrounded  with  a  delicate  film  of  water. 
How  might  the  root  hairs  take  up  this  water  ? 


water,  the  density  of  the  cell  sap  is  lessened,  and  the  cells  of  the 
epidermis  are  thus  in  a  position  to  pass  along  their  supply  of  water 
to  the  cells  next  to  them  and  nearer  to  the  center  of  the  root. 
These  cells,  in  turn,  become  less  dense  than  their  inside  neighbors, 
and  so  the  transfer  of  water  goes  on  until  the  water  at  last  reaches 
the  central  cylinder.  Here  it  is  passed  over  to  the  tubes  of  the 
woody  bundles  and  started  up  the  stem.     The  pressure  created 

^  For  an  excellent  elementary  discussion  of  osmosis  see  Moore,  Physiology  oj 
Man  and  Other  Animals.     Henry  Holt  and  Company. 


SOIL  AND   ITS   RELATION  TO   ROOTS 


77 


by  this  process  of  osmosis  is  sufficient  to  send  water  up  the  stem 
to  a  distance,  in  some  plants,  of  25  to  30  feet.  Cases  are  on 
record  of  water  having  been  raised  in  the  birch  a  distance  of  85 
feet. 

Physiological  Importance  of  Osmosis.  —  It  is  not  an  exaggera- 
tion to  say  that  osmosis  is  a  process  not  only  of  great  importance 
to  a  plant,  but  to  an  animal  as  well.  Foods  are  digested  in  the 
food  tube  of  an  animal ;  that  is,  they  are  changed  into  a  soluble 
form  so  that  they  may  pass  through  the  walls  of  the  food  tube  and 
become  part  of  the  blood.  The  inner  lining  of  part  of  the  food 
tube  is  thrown  into  millions  of  little  fingerlike  projections  which 
look  somewhat,  in  size  at  least,  like  root  hairs.  These  fingerlike 
processes  are  (unlike  a  root  hair)  made  up  of  many  cells.  But 
they  serve  the  same  purpose  as  the  root  hairs,  for  they  absorb 
liquid  food  into  the  blood.  This  process  of  absorption  is  largely 
by  osmosis.  Without  the  process  of  osmosis  we  should  be  unable 
to  use  much  of  the  food  we  eat. 

Composition  of  Soil.  —  If  we  examine  a  mass  of  ordinary  loam 
carefully,  we  find  that  it  is  composed  of  numerous  particles  of  vary- 
ing size  and  weight.  Between  these  particles,  if  the  soil  is  not  caked 
and  hard  packed,  we  can  find  tiny  spaces.  In  well-tilled  soil  these 
spaces  are  constantly  be- 
ing formed  and  enlarged. 
They  allow  air  and  water 
to  penetrate  the  soil.  If 
we  examine  soil  under  the 
microscope,  we  find  con- 
siderable water  clinging  to 
the  soil  particles  and  form- 
ing a  delicate  film  around 
each  particle.  In  this 
manner  most  of  the  water 
is  held  in  the  soil. 

How  Water  is  held  in 
Soil.  —  To  understand  what  comes  in  with  the  soil  water,  it  will 
be  necessary  to  find  out  a  little  more  about  soil.     Scientists  who 
have  made  the  subject  of  the  composition  of  the  earth  a  study, 


Inorganic  soil  is  being  formed  by  weathering. 


78 


SOIL  AND  ITS  RELATION  TO   ROOTS 


tell  us  that  once  upon  a  time  at  least  a  part  of  the  earth  was  molten. 

Later,  it  cooled  into  solid  rock.     Soil  making  began  when  the  ice 

and  frost,  working  al- 
ternately with  the  heat, 
chipped  off  pieces  of 
rock.  These  pieces  in 
time  became  ground  in- 
to fragments  by  action 
of  ice,  glaciers,  running 
water,  or  the  atmos- 
phere. This  process 
is  called  weathering. 
Weathering  is  aided  by 
oxidation.  A  glance 
at  almost  any  crum- 
bling stones  will  con- 
vince you  of  this, 
because  of  the  yellow 
oxide  of  iron  (rust) 
disclosed.  So  by  slow 
degrees  this  earth  be- 
came covered  with  a 
coating  of  what  we  call 
inorganic  soil.     Later, 


This  picture  shows  how  the  forests  help  to  cover 
the  inorganic  soil  with  an  organic  coating. 
Explain  how. 


generation  after  generation  of  tiny  plants  and  animals  which  lived 
in  the  soil  died,  and  their  remains  formed  the  first  organic  materials 
of  the  soil. 

You  are  all  familiar  with 
the  difference  between  the 
so-called  rich  soil  and  poor 
soil.  The  dark  soil  con- 
tains more  dead  plant  and 
animal  matter,  which 
forms  the  portion  called 
humus. 

Humus  contains  Or- 
ganic Matter.  —  It  is  an 


Apparatus  for  testing  the  capacity  of  soils 
to  take  in  and  retain  moisture. 


SOIL  AND  ITS   RELATION  TO   ROOTS  79 


easy  matter  to  prove  that  black  soil  contains  organic  matter,  for  if 

an  equal  weight  of  carefully  dried  humus  and  soil  from  a  sandy  road 

is  heated  red-hot  for  some  time  and 

then  re  weighed,  the  humus  will  be 

found  to  have  lost  considerably  in 

weight,  and  the  sandy  soil  to  have 

lost  very  little.      The  material  left 

after  heating  is  inorganic  material, 

the    organic    matter    having    been 

burned  out. 

Soil  containing  organic  materials 

holds  water  much  more  readily  than 

inorganic  soil,  as  a  glance  at  the 

accompanying  figure  shows.     If  we 

fill  each  of  the  vessels  with  a  given 

weight    (say    100    grams    each)    of 

gravel,  sand,  barren  soil,  rich  loam, 

leaf   mold,   and   25   grams  of   dry, 

pulverized  leaves,  then  pour  equal 

amounts  of  water  (100  c.c.)  on  each 

and  measure  all  that  runs  through,  the  water  that  has  been  re- 
tained will  represent  the  water  supply  that  plants  could  draw  on 
from  such  soil. 

The  Root  Hairs  take  more  than  Water  out  of  the  Soil.  —  If  a 
root  containing  a  fringe  of  root  hairs  is  washed  carefully,  it  will  be 
found  to  have  little  particles  of  soil  still  clinging  to  it.  Examined 
under  the  microscope,  these  particles  of  soil  seem  to  be  cemented 
to  the  sticky  surface  of  the  root  hair.  The  soil  contains,  besides 
a  number  of  chemical  compounds  of  various  mineral  substances,  — 
lime,  potash,  iron,  silica,  and  many  others,  —  a  considerable  amount 
of  organic  material.  Acids  of  various  kinds  are  present  in  the  soil. 
These  acids  so  act  upon  certain  of  the  mineral  substances  that 
they  become  dissolved  in  the  water  which  is  absorbed  by  the  root 
hairs.  Root  hairs  also  give  off  small  amounts  of  acid.  An  in- 
teresting experiment  may  be  shown  (see  Figure  on  page  80)  to 
prove  this.  A  solution  of  phenolphthalein  loses  its  color  when  an 
acid  is  added  to  it.     If  a  growing  pea  be  placed  in  a  tube  contain- 


Soil  particles  cling  to  root  hairs. 
Why? 


80 


SOIL   AND   ITS   RELATION  TO   ROOTS 


ing  some  of  this  solution  the  latter  will  quickly  change  from  a  rose 
pink  to  a  colorless  solution. 

A  Plant  needs  Mineral  Matter  to  Make  Living  Matter.  —  Liv- 
ing matter  (protoplasm),  besides  containing  the  chemical  elements 

carbon,  hydrogen,  oxygen,  and  nitrogen, 
contains  a  very  minute  proportion  of 
various  elements  which  make  up  the 
basis  of  certain  minerals.  These  are 
calcium  (lime),  sulphur,  iron,  potassium, 
magnesium,  phosphorus,  sodium,  and 
chlorine. 

That  plants  will  not  grow  well  with- 
out certain  of  these  mineral  substances 
can  be  proved  by  the  gro\vth  of  seed- 
lings in  a  so-called  nutrient  solution.^ 
Such  a  solution  contains  all  the  mineral 
matter  that  a  plant  uses  for  food.  If 
certain  ingredients  are  left  out  of  this 
I^M  WB  solution,  the  plants  placed  in  it  will  not 

VT^  ^w  live. 

i"-^-"^ — -^  r — -^rrzza —         Nitrogen  in  a  Usable  Form  necessary 
Effect  of  root  hairs  on  phenol-    for    Growth    of    Plants.  —  A    chemical 
phthaiein    solution.      The   element  needed  by  the  plant  to  make 

change    of     color    indicates  ,  .  . 

the  presence  of  acid.  protoplasm    IS    mtrogeu.     The    air    can 

be  proven  by  experiment  to  be  made 
up  of  about  four  fifths  nitrogen,  but  this  element  cannot  be  taken 
from  either  soil  water  or  air  in  a  pure  state,  but  is  usually  ob- 
tained from  the  organic  matter  in  the  soil,  where  it  exists  with 
other  substances  in  the  form  of  nitrates.  Ammonia  and  other 
organic  compounds  which  contain  nitrogen  are  changed  by  two 
groups  of  little  plants  called  bacteria,  first  into  nitrites  and  then 
nitrates.2 

^  See  Hunter's  Laboratory  Problems  in  Civic  Biology  for  list  of  ingredients. 

2  It  has  recently  been  discovered  that  under  some  conditions  these  bacteria  are 
preyed  upon  by  tiny  one-celled  animals  {protozoa)  living  in  the  soil  and  are  so  re- 
duced in  numbers  that  they  cannot  do  their  work  effectively.  If,  then,  the  soil 
i?  heated  artificially  or  treated  with  antiseptics  so  as  to  kill  the  protozoa,  the  bac- 
teria which  escape  mxiltiply  so  rapidly  as  to  make  the  land  much  richer  than  before- 


SOIL   AND  ITS  RELATION  TO  ROOTS 


81 


Relation  of  Bacteria  to  Free  Nitrogen.  —  It  Las  been  known 
since  the  time  of  the  Romans  that  the  growth  of  clover,  peas, 
beans,  and  other  legumes  in  soil  causes  it  to  become  more  favorable 
for  growth  of  other  plants.  The  reason  for  this  has  been  dis- 
covered in  late  years.  On  the 
roots  of  the  plants  mentioned 
are  found  little  swellings  or 
nodules ;  in  the  nodules  exist 
millions  of  bacteria,  which  take 
nitrogen  from  the  atmosphere 
and  fix  it  so  that  it  can  be  used 
by  the  plant ;  that  is,  they  as- 
sist in  forming  nitrates  for  the 
plants  to  use.  Only  these 
bacteria,  of  all  the  living  plants, 
have  the  power  to  take  the  free 
nitrogen  from  the  air  and  make 
it  over  into  a  form  that  can  be 
used  by  the  roots.  As  all  the 
compounds  of  nitrogen  are  used 
over  and  over  again,  first  by 
plants,  then  as  food  for  animals, 
eventually  returning  to  the  soil 
again,  or  in  part  being  turned 
into  free  nitrogen,  it  is  evident 
that  any  new  supply  of  usable 
nitrogen  must  come  by  means 
of  these  nitrogen-fixing  bac- 
teria. 

Rotation  of  Crops.  —  The  facts  mentioned  above  are  made  use 
of  by  careful  farmers  who  wish  to  make  as  much  as  possible  from 
a  given  area  of  ground  in  a  given  time.  Such  plants  as  are  hosts 
for  the  nitrogen-fixing  bacteria  are  planted  early  in  the  season. 
Later  these  plants  are  plowed  in  and  a  second  crop  is  planted. 
The  latter  grows  quickly  and  luxuriantly  because  of  the  nitrates 
left  in  the  soil  by  the  bacteria  which  lived  with  the  first  crop. 
For  this  reason,  clover  is  often  grown  on  land  in  which  it  is  pro- 

HUNTER,    CIV.   BI. 6 


Diagram  to  show  how  the  nitrogen-fixing 
bacteria  prepare  nitrogen  for  use  by 
plants;  t,  tubercles. 


82 


SOIL  AND   ITS   RELATION   TO   ROOTS 


posed  to  plant  corn,  the  nitrogen  left  in  the  soil  thus  giving  nourish- 
ment to  the  young  corn  plants.  In  scientifically  managed  farms, 
different  crops  are  planted  in  a  given  field  on  different  years  so  that 
one  crop  may  replace  some  of  the  elements  taken  from  the  soil  by 
the  previous  crop.  This  is  known  as  rotation  of  crops. ^  The 
annual  yield  of  the  average  farm  may  thus  be  greatly  increased. 

Five  of  the  elements  necessary  to  the  life  of  the  plant  which 
may  be  taken  out  of  the  soil  by  constant  use  are  calcium,  nitrogen, 
phosphorus,  potassium,  and  sulphur.     Several  methods  are  used 

by  the  farmer  to  prevent  the 
exhaustion  of  these  and  other 
raw  food  materials  from  the  soil. 
One  method  known  as  fallowing 
is  to  allow  the  soil  to  remain 
idle  until  bacteria  and  oxidation 
have  renewed  the  chemical  ma- 
terials used  by  the  plants.  This 
is  an  expensive  method,  if  land 
is  dear.  The  most  common 
method  of  enriching  soil  is  by 
means  of  fertilizing  material 
rich  in  plant  food.  Manure  is 
most  frequently  used,  but  many 
artificial     fertilizers,     most     of 


Nitrogen  in  the  soil  is  necessary  for  plants. 
Explain  from  this  diagram  how  nitro- 


gen is  put  into  the  soil  by  some  plants     which   contain   nitrogen   in   the 
and  taken  out  by  others.  . ,       .  i 

form  oi  some  nitrate,  are  used, 
because  they  can  be  more  easily  transported  and  sold.  Such  are 
ground  bone,  guano  (bird  manure),  nitrate  of  soda,  and  many 
others.  These  also  contain  other  important  raw  food  materials 
for  plants,  especially  potash  and  phosphoric  acid.  Both  of  these 
substances  are  made  soluble  so  as  to  be  taken  into  the  roots  by 
the  action  of  the  carbon  dioxide  in  the  soil. 

The  Indirect  Relation  of  this  to  the  City  Dweller.  —  All  of  us 
living  in  the  city  are  aware  of  the  importance  of  fresh  vegetables, 

1  That  crop  rotation  is  not  primarily  a  process  to  conserve  the  fertility  of  the 
soil,  but  is  a  sanitary  measure  to  prevent  infection  of  the  soil,  is  the  latest  belief 
of  the  scientist. 


SOIL  AND  ITS  RELATION  TO   ROOTS  83 

brought  in  from  the  neighboring  market  gardens.  But  we  some- 
times forget  that  our  great  staple  crops,  wheat  and  other  cereals, 
potatoes,  fruits  of  all  kinds,  our  cotton  crop,  and  all  plants  we  make 
use  of  grow  directly  in  proportion  to  the  amount  of  raw  food  ma- 
terials they  take  in  through  the  roots.  When  we  also  remember 
that  many  industries  within  the  cities,  as  mills,  bakeries,  and  the 
like,  as  well  as  the  earnings  of  our  railways  and  steamship  lines,  are 
largely  dependent  on  the  abundance  of  the  crops,  we  may  recognize 
the  importance  of  what  we  have  read  in  this  chapter. 

Food  Storage  in  Roots  of  Commercial  Importance.  —  Some  plants, 
as  the  parsnip,  carrot,  and  radish,  produce  no  seed  until  the  second 
year,  storing  food  in  the  roots  the  first  year  and  using  it  to  get  an 
early  start  the  following  spring,  so  as  to  be  better  able  to  produce 
seeds  when  the  time  comes.  This  food  storage  in  roots  is  of  much 
practical  value  to  mankmd.  Many  of  our  commonest  garden 
vegetables,  as  those  mentioned  above,  and  the  beet,  turnip,  oyster 
plant,  sweet  potato  and  many  others,  are  of  value  because  of  the 
food  stored.  The  sugar  beet  has,  in  Europe  especially,  become 
the  basis  of  a  great  industry. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Bigelow,  Applied  Biology.     The  Macmillan  Company. 

Coulter,  Plant  Life  and  Plant  Uses,  Chaps.  Ill,  IV.     American  Book  Company. 
Mayne  and  Hatch,  High  School  Agriculture.     American  Book  Company. 
Moore,  The  Physiology  of  Man  and  Other  Animals.     Henry  Holt  and  Company. 
Sharpe,  Laboratory  Manvxxl  in  Biology,  pp.  73-87.    American  Book  Company. 

ADVANCED 

Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Part  II.     Amer,  Book  Co 
Duggar,  Plant  Physiology.     The  Macmillan  Company. 
Goodale,  Physiological  Botany.     American  Book  Company. 
Green,  Vegetable  Physiology,  Chaps.  V,  VI.     J.  and  A.  Churchill. 
Kerner-Oliver,  Natural  History  of  Plants.     Henry  Holt  and  Company. 
MacDougal,  Plant  Physiology.     Longmans,  Green,  and  Company. 


VII.   PLANT  GROWTH  AND   NUTRITION  —  PLANTS 

MAKE   FOOD 

Problem,  —  Where,  wlien,  and  how  green  plants  malce  food  ? 

(a)  How  and  why  is  moisture  given  off  from  leaves  ? 

(b)  W1^at  is  the  reaction  of  leaves  to  light  ? 

(c)  What  is 'made  iiv  green  I  eaves  in  the  sunlight? 

id)    What  by-products  are  given  off  in  the  above  process  ? 
(e)  Other  functions  of  leaves. 

Laboratory  Suggestions 

Demonstration.  —  Water  given  off  by  plant  in  sunlight.     Loss  of  weight 
•due  to  transpiration  measured. 
Laboratory  exercise.  — 

(a)  Gross  structure  of  a  leaf. 

(6)  Study  of  stoma  and  lower  epidermis  under  microscope. 

(c)  Study  of  cross  section  to  show  cells  and  air  spaces. 
Demonstration.  —  Reaction  of  leaves  to  light. 
Demonstration.  —  Light  necessary  to  starch  making. 
Demonstration.  —  Air  necessary  to  starch  making. 
Demonstration.  —  Oxygen  a  by-product  of  starch  making. 

What  becomes  of  the  Water  taken  in 
by  the  Roots?  —  We  have  seen  that 
more  than  pure  water  has  been  absorbed 
through  the  root  hairs  into  the  roots. 
What  becomes  of  this  water  and  the 
other  substances  that  have  been  ab- 
sorbed? This  question  may  be  partly 
answered  by  the  following  experiments. 

Passage  of  Fluids  up  the  Stem.  —  If 
any  young  growing  shoots  (young  seed- 
lings of  corn  or  pea,  or  the  older  stems 
of  garden  balsam,  touch-me-not,  or  sun- 
flower)  are  placed  in  red  ink  (eosin), 
and  left  in  the  sun  for  a  few  hours,  the 
red  ink  will  be  found  to  have  passed  up 

the  stem.     If  such  stems  were  examined 
84 


Apple  twigs  split  to  show  the 
course  of  colored  water  up 
the  stem. 


PLANTS  MAKE  FOOD 


85 


carefully,  it  would  be  seen  that  the 
colored  fluid  is  confined  to  collections 
of  woody  tubes  immediately  under  the 
inner  bark.  Water  evidently  rises  in 
that  part  of  the  stem  we  call  the  wood. 
Water  given  off  by  Evaporation  from 
Leaves.  —  Take  some  well-watered 
potted  green  plant,  as  a  geranium  or 
hydrangea,  cover  the  pot  with  sheet 
rubber,  fastening  the  rubber  close  to 
the  stem  of  the  plant.  Next  weigh 
the  plant  with  the  pot.  Then  cover 
it  with  a  tall  bell  jar  and  place  the  ap- 
paratus in  the  sun.  In  a  few  minutes 
drops  of  moisture  are  seen  to  gather 
on  the  inside  of  the  jar.     If  we  now 

weigh  the  pot- 
ted plant,  we 
find  it  weighs 
less  than  be- 
fore. Obvi- 
ously the  loss 
comes  from  the 


Experiment  to  prove  that  water 
is  given  off  through  the  leaves 
of  a  green  plant. 


The  skeleton  of  a  leaf.  M.R., 
the  midrib;  P.,  the  leafstalk; 
v.,  the  veins. 


water  lost,  and  evidently  this  water  escapes 
as  vapor  from  either  the  stem  or  leaves. 

The  Structure  of  a  Leaf.  —  In  the  ex- 
periment with  the  red  ink  mentioned 
above  we  will  find  that  the  fluid  has  gone 
out  into  the  skeleton  or  framework  of 
the  leaf.  Let  us  now  examine  a  leaf 
more  carefully.  It  shows  usually  (1)  a 
flat,  broad  hlade^  which  may  take  almost 
any  conceivable  shape ;  (2)  a  stem  which 
spreads  out  in  the  blade  (3)  in  a  number 
of  veins. 

The  Cell  Structure  of  a  Leaf.  —  The 
under  surface  of  a  leaf  seen  under  the 


8G 


PLANTS   MAKE   FOOD 


microscope  usually  shows  numbers  of  tiny  oval  openings.  These 
are  called  stomata  (singular  stoma).  Two  cells,  usually  kidney- 
shaped,  are  found,  one  on  each  side  of  the  opening.  These  are 
the  guard  cells.  By  change  in  shape  of  these  cells  the  opening 
of  the  stoma  is  made  larger  or  smaller.  Larger  irregular  cells 
form  the  epidermis,  or  outer  covering  of  the  leaf.     Study  of  the 

leaf  in  cross  section  shows  that  these 
stomata  open  directly  into  air  chambers 
which  penetrate  between  and  around 
the  loosely  arranged  cells  composing 
the  underpart  of  the  leaf.  The  upper 
surface  of  leaves  sometimes  contains 
stomata,  but  more  often  they  are  lack- 
ing. The  under  surface  of  an  oak  leaf 
of  ordinary  size  contains  about  2,000,000 
stomata.  Under  the  upper  epidermis 
is  a  layer  of  green  cells  closely  packed 
together  (called  collectively  the  palisade 
layer).  These  cells  are  more  or  less 
columnar  in  shape.  Under  these  are 
several  rows  of  rather  loosely  placed 
cells  just  mentioned.  These  are  called 
collectively  the  spongy  tissue.  If  we 
happen  to  have  a  section  cut  through 
a  vein,  we  find  this  composed  of  a 
number  of  tubes  made  up  of,  and  strengthened  by,  thick-walled 
cells.  The  veins  are  evidently  a  continuation  of  the  tubes  of  the 
stem  out  into  the  blade  of  the  leaf. 

Evaporation  of  Water.  —  During  the  day  an  enormous  amount- 
of  water  is  taken  up  by  the  roots  and  passed  out  through  the 
leaves.  So  great  is  this  excess  at  times  that  a  small  grass  plant 
on  a  summer's  day  evaporates  more  than  its  own  weight  in  water. 
This  would  make  nearly  half  a  ton  of  water  delivered  to  the  air 
during  twenty-four  hours  by  a  grass  plot  twenty-five  by  one  hun- 
dred feet,  the  size  of  the  average  city  lot.  According  to  Ward, 
an  oak  tree  may  pass  off  two  hundred  and  twenty-six  times  its 
own  weight  in  water  during  the  season  from  June  to  October. 


Section  through  the  blade  of  a 
leaf  as  seen  under  the  com- 
pound microscope.  S,  air 
spaces,  which  communicate 
with  the  outside  air;  V,  vein 
in  cross  section;  *S.r.,  breath- 
ing hole  (stoma);  E,  outer 
layer  of  cells;  P,  green  cells. 


PLANTS  MAKE  FOOD 


87 


From  which  Surface  of  the  Leaf  is  Water  Lost  ?  —  In  order  to  find  out 
whether  water  is  passed  out  from  any  particular  part  of  the  leaf,  we  may 
remove  two  leaves  of  the  same  size  and  weight  from  some  large-leaved 
plant  ^  —  a  mullein  was  used  for  the  illustrations  given  below  —  and  cover 
the  upper  surface  of  one  leaf  and  the  lower  surface  of  the  other  with  vase- 
line. The  leaf  stalks  of  each  should  be  covered  with  wax  or  vaseline,  and 
the  two  leaves  exactly  balanced  on  the  pans  of  a  balance  which  has  pre- 
viously been  placed  in  a  warm  and  sunny  place.  Within  an  hour  the  leaf 
which  has  the  upper  surface   covered  with  vaseline  will  show  a  loss  of 


Experiment  to  show  through  which  surface  of  a  leaf  water  passes  ofif. 


weight.  Examination  of  the  surface  of  a  mullein  leaf  shows  us  that  the 
lower  surface  of  the  leaf  is  provided  with  stomata.  It  is  through  these  organs, 
then,  that  water  is  passed  out  from  the  tissues  of  the  leaf. 

Factors  in  Transpiration.  —  The  amount  of  water  lost  from  a 
plant  varies  greatly  under  different  conditions.  The  humidity 
of  the  air,  its  temperature,  and  the  temperature  of  the  plant  all 
affect  the  rate  of  transpiration.  The  stomata  also  tend  to  close 
under  some  conditions,  thus  helping  to  prevent  (evaporation.  But 
there  seems  to  be  no  certain  regulation  of  this  water  loss.  ( Conse- 
quently plants  droop  or  wilt  on  hot  dry  days  because  they  cannot 

1  The  "rubber  plant"  leaf  is  ap  easily  obtainable  and  excellent  demonstration. 


88 


PLANTS   MAKE  FOOD 


obtain  water  rapidly  enough  from  the  soil  to  make  up  for  the  loss 
through  the  leaves. 


a 


Diagrams  of  a  stoma,  a,  surface  view  of  a  closed  stoma;  b,  the  same  stoma 
opened.  (After  Hanson.)  c,  diagrams  of  a  transverse  section  through  a  stoma, 
dotted  Hnes  indicate  the  closed  position  of  the  guard  cells,  the  heavy  Hnes  the 
open  condition.     (After  Schwendener.) 

Green  Plants  Food  Makers.  —  We  have  previously  stated 
that  green  plants  are  the  great  food  makers  for  themselves  and 
for  animals.  We  are  now  ready  to  attack  the  problem  of  how 
green  plants  make  food. 

The  Sun  a  Source  of  Energy.  —  We  all  know  the  sun  is  a  source 
of  most  of  the  energy  that  is  released  on  this  earth  in  the  form  of 
heat  or  light.  Every  boy  knows  the  power  of  a  ''  burning  glass." 
Solar  engines  have  not  come  into  any  great  use  as  yet,  because 
fuel  is  cheaper,  but  some  day  we  undoubtedly  will  directly  harness 
the  energy  of  the  sun  in  everyday  work.  Actual  experiments 
have  shown  that  vast  amounts  of  energy  are  given  to  the  earth. 
When  the  sun  is  highest  in  the  sky,  energy  equivalent  to  one  hun- 
dred horse  power  is  received  by  a  plot  of  land  twenty-five  by  one 
hundred  feet,  the  size  of  a  city  lot.  Plants  receive  and  use  much 
of  this  energy  by  means  of  their  leaves. 

Effect  of  Light  on  Plants.  —  In  young  plants  which  have  been 
grown  in  total  darkness,  no  green  color  is  found  in  either  stems 
or  leaves,  the  latter  often  being  reduced  to  mere  scales.  The 
stems  are  long  and  more  or  less  reclining.  We  can  explain  the 
changed  condition  of  the  seedling  grown  in  the  dark  only  by  as- 
suming that  light  has  some  effect  on  the  protoplasm  of  the  seedling 
and  induces  the  growth  of  the  green  part  of  the  plant.  If  seedlings 
have  been  growing  on  a  window  sill,  or  where  the  light  comes  in 
from  one  side,  you  have  doubtless  noticed  that  the  stem  and  leaves 
of  the  seedlings  incline  in  the  direction  from  which  the  li^ht  comes. 


PLANTS   MAKE   FOOD 


89 


The  experiment  pictured  shows  this  effect  of  light  very  plainly. 
A  hole  was  cut  in  one  end  of  a  cigar  box  and  barriers  were  erected 
in  the  interior  of  the  box  so  that  the  seeds  planted  in  the  sawdust 
received  their  light  by  an  indirect  course.  The  young  seedling 
in  this  case  responded  to  the  influence  of  the  stimulus  of  light  so 
as  to  grow  out  finally  through  the  hole  in  the  box  into  the  open 


Two  stages  in  an  experiment  to  show  that  green  plants  grow 

toward  the  light. 


air.  This  growth  of  the  stem  to  the  light  is  of  very  great  impor- 
tance to  a  growing  plant,  because,  as  we  shall  see  later,  food  mak- 
ing depends  largely  on  the  amount  of  sunlight  the  leaves  receive. 
Effect  of  Light  on  Leaf  Arrangement.  —  It  is  a  matter  of  common 
knowledge  that  green  leaves  turn  toward  the  light.  Place  grow- 
ing pea  seedlings,  oxalis,  or  any  other  plants  of  rapid  gro^vth  near 
a  window  which  receives  full  sunlight.  Within  a  short  time  the 
leaves  are  found  to  be  in  positions  to  receive  the  most  sunlight 
possible.  Careful  observation  of  any  plant  growing  outdoors 
shows  us  that  in  almost  every  case  the  leaves  are  so  disposed  as 
to  get  much  sunlight.  The  ivy  climbing  up  the  wall,  the  morning- 
glory,  the  dandelion,  and  the  burdock  all  show  different  arrange- 
ments of  leaves,  each  presenting  a  large  surface  to  the  light. 
Lewes  are   often   definitely   arranged,    fitting   in   between  one 


90 


PLANTS   MAKE   FOOD 


another  so  as  to  present  their  upper  surface  to  the  sun.  Such  an 
arrangement  is  known  as  a  leaf  mosaic.  In  the  case  of  the  dande- 
lion, a  rosette  or  whorled  cluster  of  leaves  is  found.  In  the  horse- 
chestnut,  where  the  leaves  come  out  opposite  each  other,  the  older 
leaves  have  longer  petioles  than  the  young  ones.  In  the  mullein 
the  entire  plant  forms  a  <cone.  The  old  leaves  near  the  bottom 
have  long  stalks,  and  the  little  ones  near  the  apex  come  out  close 


A  lily,  showing  long  narrow 
leaves. 


The  dandelion,  showing  a  whorled  ar- 
rangement of  long  irregular  leaves. 


to  the  main  stalk.  In  every  case  each  leaf  receives  a  large  amount 
of  light.  Other  modifications  of  these  forms  may  easily  be  found 
on  any  field  trip. 

Starch  made  by  a  Green  Leaf.  —  If  we  examine  the  palisade 
layer  of  the  leaf,  we  find  cells  which  are  almost  cylindrical  in  form. 
In  the  protoplasm  of  such  cells  are  found  a  number  of  little  green- 
colored  bodies,  which  are  known  as  chloroplasts  or  chlorophyll 
bodies.  If  we  place  the  leaf  in  wood  alcohol,  we  find  that  the 
bodies  still  remain,  but  that  the  color  is  extracted,  going  into  the 
alcohol  and  giving  to  it  a  beautiful  green  color.  The  chloroplasts 
are,  indeed,  simply  part  of  the  protoplasm  of  the  cell  colored  green. 
These  bodies  are  of  the  greatest  importance  directly  to  plants  and 
indirectly  to  animals.     The  chloroplasts,  by  means  of  the  energy  re- 


PLANTS  MAKE  FOOD 


91 


ceived  from  the  sun,  manufacture  starch  out  of  certain  raw  materials. 
These  raw  materials  are  soil  water,  which  is  passed  up  througli 
the  bundles  of  tubes  into  the  veins  of  the  leaf  from  the  roots,  and 
carbon  dioxide,  which  is  taken  in  through  the  stomata  or  pores, 
which  dot  the  under  surface  of  the  leaf.  A  plant  with  variegated 
leaves,  as  the  coleus,  makes  starch  only  in  the  green  part  of  the 
leaf,  even  though  these  raw  materials  reach  all  parts  of  the  leaf. 

Light  and  Air  necessary  for 
Starch  Making.  —  If  we  pin  strips 
of  black  cloth,  such  as  alpaca,  over 
some  of  the  leaves  of  a  growing 
hydrangea  which  has  previously 
been  placed  in  a  dark  room  for  a 


An  experiment  to  show  the  effect  of  ex- 
cluding Hght  (but  not  air)  from  the 
leaves  of  a  green  plant.  The  result  of 
this  experiment  is  seen  in  the  next 
picture.  (Experiment  performed  by 
C.   Dobbins  and  A.  Schwartz.) 


Starchless  area  in  a  leaf  caused 
by  excluding  sunlight  by 
means  of  a  strip  of  black 
cloth. 


few  hours,  and  then  put  the  plant  in  direct  sunlight  for  an  hour 
or  two,  we  are  ready  to  test  for  starch.  We  then  remove  some  of 
the  covered  leaves  and  extract  the  chlorophyll  with  wood  alcohol 
(because  the  green  color  of  the  chlorophyll  interferes  with  the  blue 
color  of  the  starch  test).  A  test  then  shows  that  starch  is  present 
only  in  the  portions  of  the  leaves  exposed  to  sunlight.  From  this 
experiment  we  infer  that  the  sun  has  something  to  do  with  starch 
making  in  a  leaf.  The  necessity  of  a  part  of  the  air  (carbon 
dioxide)    for   starch   making  may  also  easily  be  proved,  for  the 


92 


PLANTS  MAKE  FOOD 


parts  of  leaves  covered  with  vaseline  will  be  found  to  contain  no 
starch,  while  parts  of  the  leaf  without  vaseline,  but  exposed  to  the 
sun  and  air,  do  contain  starch. 

Air  is  necessary  for  the  process  of  starch  making  in  a  leaf, 
not  only  because  carbon  dioxide  gas  is  absorbed  (there  are  from 
three  to  four  parts  in  ten  thousand  present  in  the  atmosphere), 


ogoo^O 


Diagram  to  show  starch  making.     Read  the  text  carefully  and  then  explain 

this  diagram. 

but  also  because  the  leaf  is  alive  and  must  have  oxygen  in  order  to 
do  work.     This  oxygen  it  takes  from  the  air  around  it. 

Comparison  of  Starch  Making  and  Milling.  —  The  manufacture 

of  starch  by  the  green  leaf 
is  not  easily  understood. 
The  process  has  been  com- 
pared to  the  milling  of 
grain.  In  this  case  the 
mill  is  the  green  part  of  the 
leaf.  The  sun  furnishes  the 
motive  power,  the  chloro- 
plasts  constitute  the  ma- 
chinery, and  soil  water  and 
carbon  dioxide  are  the  raw 
products  taken  into  the 
mill.  The  manufactured 
product  is  starch,^  and  a 
certain  by-product  (corre- 
sponding to  the  waste  in  a 
mill)  is  also  given  out.  This 
by-product  is  oxygen.     To 


Diagram  to  illustrate  the  formation  of 
starch  in  a  leaf. 


Sugar  is  first  manufactured  and  then  transformed  into  starch. 


PLANTS   MAKE   FOOD 


93 


understand  the  process  fully,  we  must  refer  to  a  small  portion 
of  the  leaf  shown  below.  Here  we  find  that  the  cells  of  the  green 
layer  of  the  leaf,  under  the  upper  epidermis,  perform  most  of 
the  work.  The  carbon  dioxide  is  taken  in  through  the  stomata 
and  reaches  the  green  cells  by  way  of  the  intercellular  spaces  and 
by  osmosis  from  cell  to  cell.  Water  reaches  the  green  cells 
through  the  veins.  It  then  passes  into  the  cells  by  osmosis,  and 
there  becomes  part  of  the  cell  sap.  The  light  of  the  sun  easily 
penetrates  to  the  cells  of  the  palisade  layer,  giving  the  energy 

LIGHT 


I 


Soil  water 


Diagram  (after  Stevens)  to  illustrate  the  processes  of  breathing  and  food 
making  in  the  cells  of  a  green  leaf  in  the  sunlight. 

needed  to  make  the  starch.  This  whole  process  is  a  very  delicate 
one,  and  will  take  place  only  when  external  conditions  are  favorable. 
For  example,  too  much  heat  or  too  little  heat  stops  starch  making 
in  the  leaf.  This  building  up  of  food  and  the  release  of  oxygen 
by  the  plant  in  the  presence  of  sunlight  is  called  photosynthesis. 

Manufacture  of  Fats.  —  Inasmuch  as  tiny  droplets  of  oil  are 
found  inside  the  chlorophyll  bodies  in  the  leaf,  we  believe  that  fats, 
too,  are  made  there,  probably  by  a  transformation  of  the  starch 
already  manufactured. 

Protein  Making  and  its  Relation  to  the  Making  of  Living  Matter. 
—  Protein  material  is  a  food  which  is  necessary  to  form  protoplasm. 


94 


PLANTS  MAKE  FOOD 


Protein  food  is  present  in  the  leaf,  and  is  found  in  the  stem  or  root 
as  well.  Proteins  can  apparently  be  manufactured  in  any  of  the 
cells  of  green  plants,  the  presence  of  light  not  seeming  to  be  a  nec- 
essary factor.  How  it  is  manufactured  is  a  matter  of  conjecture. 
The  minerals  brought  up  in  the  soil  water  form  part  of  its  composi- 
tion, and  starch  or  grape  sugar  give  three  elements  (C,  H,  and  0). 
The  element  nitrogen  is  taken  up  by  the  roots  as  a  nitrate  (nitrogen 
in  combination  with  lime  or  potash).     Proteins  are  probably  not 

made  directly  into  protoplasm 
in  the  leaf,  but  are  stored  by 
the  cells  of  the  plant  and  used 
when  needed,  either  to  form 
new  cells  in  growth  or  to  re- 
pair waste.  While  plants  and 
animals  obtain  their  food  in 
different  ways,  they  probably 
make  it  into  living  substance 
{assimilate  it)  in  exactly  the 
same  manner. 

Foods  serve  exactly  the  same 
purposes  in  plants  and  in  ani- 
mals ;  they  either  build  living 
matter  or  they  are  burned 
(oxidized)  to  furnish  energy 
(power  to  do  work).  If  you 
doubt  that  a  plant  exerts 
energy,  note  how  the  roots  of 
a  tree  bore  their  way  through 
the  hardest  soil,  and  how  stems  or  roots  of  trees  often  split  open 
the  hardest  rocks,  as  illustrated  in  the  figure  above. 

Starch-Making  and  its  Relation  to  Human  Welfare.  —  Leaves 
which  have  been  in  darkness  show  starch  to  be  present  soon  after 
exposure  to  light.  A  corn  plant  sends  10  to  15  grams  of  reserve 
material  into  the  ears  in  a  single  day.  The  formation  of  fruit,  and 
especially  the  growth  of  the  grain  fields,  show  the  economic  im- 
portance of  this  fact.  Not  only  do  plants  make  their  own  food 
and  store  it  away,  but  they  make  food  for  animals  as  well.     And 


An  example  of  how  a  tree  may  exert 
energy.  This  rock  has  been  split  by 
the  growing  tree. 


PLANTS  MAKE  FOOD 


95 


the  food  is  stored  in  such  a  stable  form  that  it  may  be  sent  to  all 
parts  of  the  world  in  the  form  of  grain  or  other  fruits.  Animals, 
herbivorous  and  flesh-eating,  man  himself,  all  are  dependent  upon 
the  starch-making  processes  of  the  green  plant  for  the  ultimate 
source  of  their  food.  When  we  remember  that  in  1913  in  the 
United  States  the  total  value  of  all  farm  crops  was  over 
$6,000,000,000,  and  when  we  realize  that  these  products  came  from 
the  air  and  soil  through  the  energy  of  the  sun,  we  may  begin  to 
realize  why  as  city  boys  and  girls  the  study 
of  plant  biology  is  of  importance  to  us. 

Green  Plants  give  off  Oxygen  in  Sun- 
light. —  In  still  another  way  green  plants 
are  of  direct  use  to  us  in  the  city.  Dur- 
ing this  process  of  starch-making  oxygen 
is  given  off  as  a  by-product.  This  may 
easily  be  proven  by  the  following  experi- 
ment.^ Place  any  green  water  plant  in  a 
battery  jar  partly  filled  with  water,  cover 
the  plants  with  a  glass  funnel  and  mount 
a  test  tube  full  of  water  over  the  mouth  of 
the  funnel.  Then  place  the  apparatus  in  a 
warm  sunny  window.  Bubbles  of  gas  are 
seen  to  rise  from  the  plant.  After  two  or 
three  hours  of  hot  sun,  enough  of  the  gas 
can  be  obtained  by  displacement  of  the 
water  to  make  the  oxygen  test. 

That  oxygen  is  given  off  as  a  by-product 
by  green  plants  is  a  fact  of  far-reaching   Experiment  to  show  that 
importance.     City  parks  are  true  ' '  breath-      ^^^^^^^ , ^^  ^-^^^^^^  ,^f 

^  '^   ^  ^  green  plants  in  the  sun- 

ing  spaces."      The  green  covering  of  the       light. 

earth  is  giving  to  animals  an  element  that 

they  must  have,  while  the  animals  in  their  turn  are  supplying  to 

the  plants  carbon  dioxide,   a  compound   used   in   food-making. 

Thus  a  widespread  relation  of  mutual  heli:)fulness  exists  between 

plants  and  animals. 

1  Immediate  success  with  this  experiment  will  be  obtained  if  the  water  has  been 
previously  charged  with  carbon  dioxide. 


96  PLANTS   MAKE   FOOD 

Respiration  by  Leaves.  —  All  living  things  require  oxygen.  It 
is  by  means  of  the  oxidation  of  food  materials  within  the  plant's 
body  that  the  energy  used  in  growth  and  movement  is  released. 
A  plant  takes  in  oxygen  largely  through  the  stomata  of  the  leaves, 
to  a  less  extent  through  the  lenticels  or  breathing  holes  in  the  stem, 
and  through  the  roots.  Thus  rapidly  growing  tissues  receive  the 
oxygen  necessary  for  them  to  perform  their  work.  The  products 
of  oxidation  in  the  form  of  carbon  dioxide  are  also  passed  off 
through  these  same  organs.  It  can  be  shown  by  experiment  that 
a  plant  uses  up  oxygen  in  the  darkness ;  in  the  light  the  amount 
of  oxygen  given  off  as  a  by-product  in  the  process  of  starch-making 
is,  of  course,  much  greater  than  the  amount  used  by  the  plant. 

Summary.  —  From  the  above  paragraphs  it  is  seen  that  a  leaf 
performs  the  following  functions :  (1)  breathing,  or  the  taking  in 
of  oxygen  and  passing  off  of  carbon  dioxide ;  (2)  starch-making, 
with  the  incidental  passing  out  of  oxygen ;  (3)  formation  of  proteins, 
with  their  digestion  and  assimilation  to  form  new  tissues;  and 
(4)  the  transpiration  of  water. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Andrews,  A  Practical  Course  in  Botany,  pages  160-177.     American  Book  Company. 
Coulter,  A  Textbook  of  Botany,  pages  5-40.     D.  Appleton  and  Company. 
Covilter,  Plant  Life  and  Plant  Uses.     American  Book  Company. 
Dana,  Plants  and  their  Children,  pages  135-185.     American  Book  Company. 
Sharpe,  A  Laboratory  Manual  in  Biology,  pages  90-102.     American  Book  Company. 
Stevens,  Introduction  to  Botany,  pages  81-99.     D.  C.  Heath  and  Company. 

ADVANCED 

Clement,  Plant  Physiology  and  Ecology.     Henry  Holt  and  Company. 

Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Part  II,  and  Vol.  II.     American 

Book  Company. 
Darwin,  Insectivorous  Plants.     D.  Appleton  and  Company. 
Duggar,  Plant  Physiology.     The  Mj*cmillan  Company. 
Goodale,    Physiological   Botany,    pages    337-353    and   409^24.     American    Book 

Company. 
Green,  Vegetable  Physiology.     J.  and  A.  Churchill. 

Lubbock,  Flowers,  Fruits,  and  Leaves,  last  part.     The  Macmillan  Company. 
MacDougal,    Practical    Textbook    of  Plant    Physiology.     Longmans,    Green,    and 

Company. 
Report  of  the  Division  of  Forestry,  U.  S.  Department  of  Agricultuie,  1899. 
Ward,  The  Oak.     D.  Appleton  and  Company. 


VIII.     PLANT  GROWTH  AND  NUTRITION  — THE   CIR- 
CULATION AND  FINAL  USES  OF  FOOD  BY  PLANTS 

Problem.  —  How  green   plants   store  and  use  the  food  thei 
niahe. 

id)    What  are  the  organs  of  circulation  ? 

{h)  How  and  where  does  food  circulate  ? 

(c)  How  does  the  plant  assimilate  its  food? 

Laboratory  Suggestions 

Laboratory  exercise.  —  The  structure  (cross  section)  of  a  woody  stem. 

Demonstration.  —  To  show  that  food  passes  downward  in  the  bark. 
Demonstration.  —  To  show  the  condition  of  food  passing  through  the 
stem. 

Demonstration.  —  Plants  with  special  digestive  organs. 

The  Circulation  and  Final  Uses  of  Foods  in  Green  Plants.  —  We 

have  seen  that  cells  of  green  plants  make  food  and  that  such  cells 
are  mostly  in  the  leaves.  But  all  parts  of  the  bodies  of  plants  grow. 
Roots,  stems,  leaves,  flowers,  and  fruits  grow.  Seeds  are  store- 
houses of  food.  We  must  now  examine  the  stem  of  some  plant  in 
order  to  see  how  food  is  distributed,  stored,  and  finally  used  in  the 
various  parts  of  the  plant. 

The  Structure  of  a  Woody  Stem.  —  If  we  cut  a  cross  section 
through  a  young  willow  or  apple  stem,  we  find  it  shows  three 
distinct  regions.  The  center  is  occupied  by  the  spongy,  soft  pith; 
surrounding  this  is  found  the  rather  tough  wood,  while  the  outer- 
most area  is  hark.  More  careful  study  of  the  bark  reveals  the 
presence  of  three  layers  —  an  outer  layer,  a  middle  green  layer, 
and  an  inner  fibrous  layer,  the  latter  usually  brown  in  color.  This 
layer  is  made  up  largely  of  tough  fiberlike  cells  known  as  hast 
fibers.  The  most  important  parts  of  this  inner  bark,  so  far  as  the 
plant  is  concerned,  are  many  tubelike  structures  known  as  sieve 
tuhes.    These  are  long  rows  of  living  cells,  having  perforated 

HUNTER,  CIV.  BI.  —  7  97 


98      CIRCULATION  AND   USES  OF  FOOD   BY  PLANTS 


sievelike  ends.     Through  these  cells  food  materials  pass  downward 
from  the  upper  part  of  the  plant,  where  they  are  manufactured. 

In  the  wood  will  be  noticed  (see  Figure)  a  number  of  lines  radiat- 
ing outward  from  the  pith  toward  the  bark.  These  are  thin  plates 
of  pith  which  separate  the  wood  into  a  number  of  wedge-shaped 
masses.     These  masses  of  wood  are  composed  of  many  elongated 

cells,  which,  placed  end  to  end, 
form  thousands  of  little  tubes 
connecting  the  leaves  with  the 
roots.  In  addition  to  these  are 
many  thick-walled  cells,  which 
give  strength  to  the  mass  of 
wood.  The  bundles  of  tubes 
with  their  surrounding  hard 
walled  cells  are  the  continua- 
tion of  the  bundles  of  tubes 
which  are  found  in  the  root. 
In  sections  of  wood  which  have 
taken  several  years  to  grow, 
we  find  so-called  annual  rings. 
The  distance  between  one  ring 
and  the  next  (see  Figure)  usu- 
ally represents  the  amount  of 
growi^h  in  one  year.  Growth 
takes  place  from  an  actively  dividing  layer  of  cells,  knowTi  as  the 
cambium  layer.  This  layer  forms  wood  cells, from  its  inner  surface 
and  bark  from  its  outer  surface.  Thus  new  wood  is  formed  as  a 
distinct  ring  around  the  old  wood. 

Use  of  the  Outer  Bark.  —  The  outer  bark  of  a  tree  is  protective. 
The  cells  are  dead,  the  heavy  woody  skeletons  serving  to  keep  out 
cold  and  dryness,  as  well  as  prevent  the  evaporation  of  fluids  from 
within.  The  bark  also  protects  the  tree  from  attack  of  other 
plants  or  animals  which  might  harm  it.  Most  trees  are  provided 
with  a  layer  of  corky  cells.  This  layer  in  the  cork  oak  is  thick 
enough  to  be  of  commercial  importance.  The  function  of  the 
corky  layer  in  preventing  evaporation  is  well  seen  in  the  case  of 
the  potato,  which  is  a  .true  stem,  though  found  underground.     If 


Section  of  a  twig  of  box  elder  three  years 
old,  showing  three  annual  growth  rings. 
The  radiating  lines  (m)  which  cross  the 
wood  {w)  represent  the  pith  rays,  the 
principal  ones  extending  from  the  pith 
in  the  center  to  the  cortex  or  bark. 
(From  Coulter's  Plant  Relations.) 


CIRCULATION  AND   USES   OF  FOOD  BY  PLANTS      99 


two  potatoes  of  equal  weight  are  balanced  on  the  scales,  the  skin 
having  been  peeled  from  one,  the  peeled  potato  will  be  found  to 
lose  weight  rapidly.  This  is  due  to  loss  of  water,  which  is  held  in 
by  the  skin  of  the  unpeeled  potato  (see  right  hand  figure  below). 

There  are  also  small  breathing  holes  known  as  lenticels  scattered 
through  the  surface  of  the  bark.  These  can  easily  be  seen  in  a 
young  woody  stem  of  apple,  beech,  or  horse-chestnut. 


Experiment  to  show  that  the  skin  of  the  potato  (a  stem)  retards  evaporation. 

Proof  that  Food  passes  down  the  Stem,  —  If  freshly  cut  willow 
twigs'  are  placed  in  water,  roots  soon  begin  to  develop  from  that 
part  of  the  stem  which  is  under  water.  If  now  the  stem  is  girdled 
by  removing  the  bark  in  a  ring  just  above  where  the  roots  are 
growing,  the  latter  will  eventually  die,  and  new  roots  ^^dll  appear 
above  the  girdled  area.  The  food  material  necessary  for  the  out- 
growth of  roots  evidently  comes  from  above,  and  the  passage  of 
food  materials  takes  place  in  a  downward  direction  just  outside 
the  wood  in  the  layer  of  bark  which  contains  the  bast  fibers  and 
sieve  tubes.  This  experiment  with  the  willow  explains  why  it  is 
that  trees  die  when  girdled  so  as  to  cut  the  sieve  tubes  of  the  inner 
bark.  The  food  supply  is  cut  off  from  the  protoplasm  of  the  cells 
in  the  part  of  the  tree  below  the  cut  area.  Many  of  the  canoe 
birches  of  our  Adirondack  forest  are  thus  killed,  girdled  by  thought- 


100    CIRCULATION   AND   USES   OF  FOOD   BY  PLANTS 


Experiment  to  show  that 
food  material  passes 
down  in  the  inner  bark. 


less  visitors.     In  the  same  manner  mice  and  other  gnawing  ani- 
mals kill  fruit  trees.     Food  substances  are  also  conducted  to  a 

much  less  extent  in  the  wood  itself,  and  food 
passes  from  the  inner  bark  to  the  center  of 
the  tree  by  way  of  the  pith  plates.  This  can 
be  proved  by  testing  for  starch  in  the  pith 
plates  of  young  stems.  It  is  found  that 
much  starch  is  stored  in  this  part  of  the  tree 
trunk. 

In  what  Form  does  Food  pass  through 
the  Stem  ?  —  We  have  already  seen  that 
materials  in  solution  (those  substances  which 
will  dissolve  in  the  water)  will  pass  from  cell 
to  cell  by  the  process  of  osmosis.  This  is 
shown  in  the  experiment  illustrated  in  the 
figure.  Two  thistle  tubes  are  partly  filled, 
one  with  starch  and  water,  the  other  with 
sugar  and  water,  and  a  piece  of  parchment 
paper  is  tied  over  the  end  of  each.      The 

lower  ends  of  both  tubes  are  placed  in  a  glass  dish  under  water. 

After  twenty-four  hours,  the  water  in  the  dish  is  tested  for  starch, 

and  then  for  sugar.     We  find  that  only  the  sugar,  which  has  been 

dissolved  by  the  water,  can  pass 

through  the  membrane. 

Digestion.  — Much  of  the  food 

made  in  the  leaves   is   stored  in 

the  form  of  starch.     But  starch, 

being  insoluble,  cannot  be  passed 

from  cell  to  cell  in  a  plant.      It 

must   be    changed    to    a    soluble 

form,  for  otherwise  it  could  not     ~' 

pass    through    the    delicate    cell 

membranes.     This  is  accomplished 

by  the  process  of  digestion.     We 

have  already  seen  that  starch  is 

changed    to     grape     sugar     in     the     Experiment  to  show  osmosis  of  sugar 

.  (right  hand  tube)  and  non-osmoses 

corn  by  the  action  of  a  substance         of  starch  (left  hand  tube). 


CIRCULATION  AND   USES  OF  FOOD   BY  PLANTS     101 


(an  enzyme)  oalled  diastase.  This  process  of  digestion  seemingly 
may  take  place  in  all  living  parts  of  the  plant,  although  most  of 
it  is  done  in  the  leaves.  In  the  bodies  of  all  animals,  including 
man,  starchy  foods  are  changed  in  a  similar  manner,  but  by 
other  enzymes,  into  soluble  grape  sugar. 

The  food  material  may  be  passed  in  a  soluble  form  until  it  comes 
to  a  place  where  food  storage  is  to  take  place,  then  it  can  be  trans- 
formed to  an  insoluble  form  (starch,  for  example) ;  later,  when 
needed  by  the  plant  in  growth,  it  may  again  be  transformed  and  sent 
in  a  soluble  form  through  the  stem  to  the  place  where  it  will  be  used. 

In  a  similar  manner,  protein  seems  to  be  changed  and  trans- 
ferred to  various  parts  of  the  plant.  Some  forms  of  protein  sub- 
stance are  soluble  and  others  insoluble  in  water.  White  of  egg,  for 
example,  is  slightly  soluble,  but  can  be  rendered  insoluble  by  heat- 
ing it  so  that  it  coagulates.  Insoluble  proteins  are  digested  within 
the  plant ;  how  and  where  is  but  slightly  understood.  In  a  plant, 
soluble  proteins  pass  down  the  sieve 
tubes  in  the  bast  and  then  may  be  stored 
in  the  bast  or  medullary  rays  of  the  wood 
in  an  insoluble  form,  or  they  may  pass 
into  the  fruit  or  seeds  of  a  plant,  and  be 
stored  there. 

What  forces  Water  up  the  Stem.  —  We 
have  seen  that  the  process  of  osmosis  is 
responsible  for  taking  in  soil  water,  and 
that  the  enormous  absorbing  surface  ex- 
posed by  the  root  hairs  makes  possible 
the  absorption  of  a  large  amount  of  water. 
Frequently  this  is  more  than  the  weight 
of  the  plant  in  every  twenty-four  hours. 

Experiments  have  been  made  which 
show  that  at  certain  times  in  the  year 
this  water  is  in  some  way  forced  up  the 
tiny  tubes   of   the   stem.      During   the 

spring  season,  in  young  and  rapidly  growing  trees,  water  has  been 
proved  to  rise  to  a  height  of  nearly  ninety  feet.  The  force  that 
causes  this  rise  of  water  in  stems  is  known  as  root  pressure. 


Diagram  to  show  the  areas 
in  a  plant  through  which 
the  raw  food  materials  pass 
up  the  stem  and  food  ma- 
terials pass  down. 


102    CIRCULATION  AND  USES  OF  FOOD  BY  PLANTS 

The  greatest  factor,  however,  is  transpiration  of  water  from 
leaves.  This  evaporation  of  water  in  the  form  of  vapor  seems  to 
result  in  a  kind  of  suction  on  the  column  of  water  in  the  stem.  In 
the  fall,  after  the  leaves  have  gone,  much  less  water  is  taken  in  by 
roots,  showing  that  an  intimate  relation  exists  between  the  leaves 
and  the  root. 

Summary  of  the  Functions  of  Green  Plants.  —  The  processes 
which  we  have  just  described  (with  the  exception  of  food  making) 
are  those  which  occur  in  the  lives  of  any  plant  or  animal.  All 
plants  and  animals  breathe,  they  oxidize  their  foods  to  release 
energy,  carbon  dioxide  being  given  off  as  the  result  of  the  union  of 
the  carbon  in  the  foods  with  the  oxygen  of  the  air.  Both  plants 
and  animals  digest  their  food ;  plants  may  do  this  in  the  cells  of 
the  root,  stem,  and  leaf.  Digestion  must  always  occur  so  that  food 
can  be  moved  in  a  soluble  condition  from  cell  to  cell  in  the  plant's 
body. 

Plants  with  Special  Digestive  Organs.  —  Some  plants  have 
special  organs  of  digestion.  One  of  these,  the  sundew,  has  leaves 
which  are  covered  on  one  side  with  tiny  glandular  hairs.     These 


Leaf  of  sundew  closing  over 
a  captured  insect. 


The  Venus  fly  trap,  showing  open 
and  closed  leaves. 


attract  insects  and  later  serve  to  catch  and  digest  the  nitrogenous 
matter  of  these  insects  by  means  of  enzymes  poured  out  by  the 
same  hairs.  Another  plant,  the  Venus  fly  trap,  catches  insects 
in  a  sensitive  leaf  which  folds  up  and  holds  the  insect  fast  until 
enzymes  poured  out  by  the  leaf  slowly  digest  it.     Still  others, 


CIRCULATION  AND  USES   OF  FOOD   BY  PLANTS     103 

called  pitcher  plants,  use  as  food  the  decayed  bodies  of  insects 
which  fall  into  their  cuplike  leaves  and  die  there.  In  this  respect 
plants  are  like  those  animals  which  have  certain  organs  in  the 
body  set  apart  for  the  digestion  of  food. 

Assimilation.  —  The  assimilation  of  foods,  or  making  of  foods 
into  living  matter,  is  a  process  we  know  very  little  about.  We 
know  it  takes  place  in  the  living  cells  of  plants  and  animals.  But 
how  foods  are  changed  into  living  matter  is  one  of  the  mysteries 
of  life  which  we  have  not  yet  solved. 

Excretion.  —  The  waste  and  repair  of  living  matter  seems  to 
take  place  in  both  plants  and  animals.  When  living  plants 
breathe,  they  give  off  carbon  dioxide.  In  the  process  of  starch- 
making,  oxygen  might  be  considered  the  waste  product.  Water 
is  evaporated  from  leaves  and  stems.  The  leaves  fall  and  carry 
away  waste  mineral  substances  which  they  contain. 

Reproduction.  —  Finally,  both  plants  and  animals  have  organs 
of  reproduction.  We  have  seen  that  the  flower  gives  rise,  after 
pollination,  to  a  fruit  which  holds  the  seeds.     These  seeds  hold 


The  embryos  of  (a)  the  morning  glory,  (b)  the  barberry,  (c)  the  potato,  (d)  the 
four  o'clock,  showing  the  position  of  their  food  supply.     (After  Gray.) 

the  embryo.  Thus  the  young  plant  is  doubly  protected  for  a  time 
and  is  finally  thrown  off  in  the  seed  with  enough  food  to  give  it  a 
start  in  life.  In  much  the  same  way  we  will  find  that  animals 
reproduce,  either  by  laying  eggs  which  contain  an  embryo  and  food 
to  start  it  in  life  or,  as  in  the  higher  animals,  by  holding  and  pro- 
tecting the  embryo  within  the  body  of  the  mother  until  it  is  born, 
a  helpless  little  creature,  to  be  tenderly  nourished  by  the  mother 
until  able  to  care  for  itself. 

The  Life  Cycle.  —  Ultimately  both  plants  and  animals  grow 
old  and  die.     Some  plants,  for  example  the  pea  or  bean,  live  but 


104    CIRCULATION   AND   USES   OF   FOOD   BY  PLANTS 

a  season ;  others,  such  as  the  big  trees  of  California,  live  for  hun- 
dreds of  years.  Some  insects  exist  as  adults  but  a  day,  while  the 
elephant  is  said  to  live  almost  two  hundred  years.  The  span  of 
life  from  the  time  the  plant  or  animal  begins  to  grow  until  it  dies 
is  known  as  the  life  cycle. 

Reference  Books 

elementary 

Hunter,  Laboratory  Probleyns  in  Civic  Biology.     American  Book  Company. 
Andrews,  A  Practical  Course  in  Botany,  pages  112-127.    American  Book  Company. 
Atkinson,  First  Studies  of  Plant  Life,  Chaps.  IV,  V,  VI,  VIII,  XXI.     Ginn. 
Coulter,  Plant  Life  and  Plant  Uses,  Chap.  V.     American  Book  Company. 
Dana,  Plants  and  their  Children,  pages  99-129.     American  Book  Company, 
Mayne  and  Hatch,  High  School  Agriculture.     American  Book  Company. 
Hodge,  Nature  Study  and  Life,  Chaps.  IX,  X,  XI.     Ginn  and  Company. 
MacDougal,  The  Nature  and  Work  of  Plants.     The  Macmillan  Company. 

ADVANCED 

Apgar,  Trees  of  the  United  States,  Chaps.  II,  V,  VI.     American  Book  Company. 
Coulter,   Barnes,   and   Cowles,   A    Textbook  of  Botany,   Vol.   I.     American  Book 

Company. 
Duggar,  Plant  Physiology.     The  Macmillan  Company. 
Ganong,  The  Teaching  Botanist.     The  Macmillan  Company. 
Goebel,  Organography  of  Plants,  Part  V.     Clarendon  Press. 
Goodale,  Physiological  Botany.     American  Book  Company. 
Gray,  Structural  Botany,  Chap.  V.     American  Book  Company,    t 
Kerner-Oliver,  Natural  History  of  Plants.     Henry  Holt  and  Company. 
Strasburger,  Noll,  Schenck,  and  Karston,  A  Textbook  of  Botany.     The  Macmillan 

Company. 
Ward,  The  Oak.     D.  Appleton  and  Company. 
Yearbook,  U.  S.  Department  of  Agriculture,  1894,  1895.  1898-1910. 


IX.     OUR   FORESTS,    THEIR   USES   AND   THE   NECES- 
SITY FOR   THEIR  PROTECTION 

Proble^n.  —Man's  relations  to  forests. 

{a)    What  is  the  value  of  forests  to  man? 

(Jb)    What  can  inan  do  to  prevent  forest  destruction  ? 

Laboratory  Suggestions 

Demonstration  of  some  uses  of  wood.  Optional  exercise  on  structure 
of  wood.  Method  of  cutting  determined  by  examination.  Home  work 
on  study  of  furniture  trim,  etc. 

Visit  to  Museum  to  study  some  economic  uses  of  wood. 

Visit  to  Museum  or  field  trip  to  learn  some  common  trees. 

The  Economic  Value  of  Trees.  Protection  and  Regulation  of 
Water  Supply.  —  Trees  form  a  protective  covering  for  parts  of 


A  forest  in  North  Carolina.     (U.  S.  G.  '6.) 

105 


i06 


OUR   FORESTS 


Working  to  prevent  erosion  after  the  removal 
of  the  forest  in  the  French  Alps. 


the  earth's  surface.  They  prevent  soil  from  being  washed  away, 
and  they  hold  moisture  in  the  ground.  The  devastation  of  im- 
mense areas  in  China  and 
considerable  damage  by 
floods  in  parts  of  Switzer- 
land, France,  and  in  Penn- 
sylvania has  resulted  where 
the  forest  covering  has 
been  removed.  No  one 
who  has  tramped  through 
our  Adirondack  forest  can 
escape  noticing  the  differ- 
ences in  the  condition  of 
streams  surrounded  by 
forest  and  those  which 
flow  through  areas  from 
which  trees  have  been  cut.  The  latter  streams  often  dry  up 
entirely  in  hot  weather,  while  the  forest-shaded  stream  has  a 
never  failing  supply  of  crystal  water. 

The  city  of  New  York  owes  much  of  its  importance  to  its  posi- 
tion at  the  mouth  of  a  great  river  with  a  harbor  large  enough  to 
float  the  navies  of  the 
world.  This  river  is 
supplied  with  water 
largely  from  the  Adi- 
rondack and  Catskill 
forests.  Should  these 
forests  be  destroyed,  it 
is  not  impossible  that 
the  frequent  freshets 
which  would  follow 
would  so  fill  the  Hud- 
son River  with  silt  and 
debris  that  the  ship 
channels   in   the   bay, 

already  costing  the  government  hundreds  of  thousands  of  dollars 
a  year  to  keep  dredged,  would  become  too  shallow  for  ships.     If 


V^i^: 


/ 


#- 


,/-' 


■      -^^ 


-■'  -• 


,'t 


^: 


/^ 


..c- 


Erosion  at  Sayre,  Pennsylvania,  by  the  Chemung 
River.     (Photograph  by  W.  C.  Barbour.) 


OUR  FORESTS  107 

this  should  occur,  the  greatest  city  in  this  .country  would  soon 
lose  its  place  and  become  of  second-rate  importance. 

The  story  of  how  this  very  thing  happened  to  the  old  Greek 
city  of  Poseidonia  is  graphically  told  in  the  following  lines  :  — 

"  It  was  such  a  strange,  tremendous  story,  that  of  the  Greek  Poseidonia, 
later  the  Roman  Psestum.  Long  ago  those  adventuring  mariners  from 
Greece  had  seized  the  fertile  plain,  which  at  that  time  was  covered  with 
forests  of  great  oak  and  watered  by  two  clear  and  shining  rivers.  They 
drove  the  Italian  natives  back  into  the  distant  hills,  for  the  white  man's 
burden  even  then  included  the  taking  of  all  the  desirable  things  that  were 
being  wasted  by  incompetent  natives,  and  they  brought  over  colonists  — 
whom  the  philosophers  and  moralists  at  home  maligned,  no  doubt, 
in  the  same  pleasant  fashion  of  our  own  day.  And  the  colonists  cut 
down  the  oaks,  and  plowed  the  land,  and  built  cities,  and  made  harbors, 
and  finally  dusted  their  busy  hands  and  busy  souls  of  the  grime  of  labor  and 
wrought  splendid  temples  in  honor  of  the  benign  gods  who  had  given  them 
the  possessions  of  the  Italians  and  filled  them  with  power  and  fatness. 

"  Every  once  in  so  often  the  natives  looked  lustfully  down  from  the  hills 
upon  this  fatness,  made  an  armed  snatch  at  it,  were  driven  back  with  bloody 
contumely,  and  the  heaping  of  riches  upon  riches  went  on.  And  more  and 
more  the  oaks  were  cut  down  —  mark  that !  for  the  stories  of  nations 
are  so  inextricably  bound  up  with  the  stories  of  trees  —  until  all  the  plain 
was  cleared  and  tilled ;  and  then  the  foothills  were  denuded,  and  the  wave 
of  destruction  crept  up  the  mountain  sides,  and  they,  too,  were  left  naked 
to  the  sun  and  the  rains. 

''  At  first  these  rains,  sweeping  down  torrentially,  unhindered  by  the 
lost  forests,  only  enriched  the  plain  with  the  long-hoarded  sweetness  of 
the  trees ;  but  by  and  by  the  living  rivers  grew  heavy  and  thick,  vomiting 
mud  into  the  ever  shallowing  harbors,  and  the  land  soured  with  the  un- 
drained  stagnant  water.  Commerce  turned  more  and  more  to  deeper 
ports,  and  mosquitoes  began  to  breed  in  the  brackish  soil  that  was  making 
fast  between  the  city  and  the  sea. 

"  Who  of  all  those  powerful  landowners  and  rich  merchants  could  ever 
have  dreamed  that  little  buzzing  insects  could  sting  a  great  city  to  death  ? 
But  they  did.  Fevers  grew  more  and  more  prevalent.  The  malaria 
haunted  population  went  more  and  more  languidly  about  their  business. 
The  natives,  hardy  and  vigorous  in  the  hills,  were  but  feebly  repulsed. 
Carthage  demanded  tribute,  and  Rome  took  it,  and  changed  the  city's 
name  from  Poseidonia  to  Psestum.      After  Rome  grew  weak,  Saracen 


108 


OUR  FORESTS 


corsairs  came  in  by  sea.  and  grasped  the  slackly  defended  riches,  and  the 
httle  winged  poisoners  of  the  night  struck  again  and  again,  until  grass 
grew  in  the  streets,  and  the  wharves  crumbled  where  they  stood.  Finally, 
the  wretched  remnant  of  a  great  people  wandered  away  into  the  more 
wholesome  hills,  the  marshes  rotted  in  the  heat  and  grew  up  in  coarse 
reeds  where  corn  and  vine  had  flourished,  and  the  city  melted  back  into 
the  wasted  earth."  ^ 

Prevention  of  Erosion  by  Covering  of  Organic  Soil.  —  We  have 
shown  how  ungoverned  streams  might  dig  out  soil  and  carry  it 


Result  of  deforestation  in  China.     This  land  has  been  ruined  by  erosion. 
^  (Carnegie  Institution  Research  in  China.) 

far  from  its  original  source.  Examples  of  what  streams  have  done 
may  be  seen  in  the  deltas  formed  at  the  mouths  of  great  rivers. 
The  forest  prevents  this  by  holding  the  water  supply  and  letting  it 
out  gradually.  This  it  does  by  covering  the  inorganic  soil  with 
humus  or  decayed  organic  material.     In  this  way  the  forest  floor 

1  Elizabeth  Bisland  and  Anne  Hoyt,  Seekers  in  Sicily.    John  Lane  Company. 


OUR  FORESTS 


109 


becomes  like  a  sponge,  holding  water  through  long  periods  of 
drought.  The  roots  of  the  trees,  too,  help  hold  the  soil  in  place. 
The  gradual  evaporation  of  water  through  the  stomata  of  the  leaves 
cools  the  atmosphere,  and  this  tends  to  precipitate  the  moisture 
in  the  air.  Eventually  the  dead  bodies  of  the  trees  themselves  are 
added  to  the  organic  covering,  and  new  trees  take  their  place. 

Other  Uses  of  the  Forest.  —  In  some  localities  forests  are  used 
as  windbreaks  and  to  protect  mountain  towns  against  avalanches. 


The  forest  regions  of  the  United  States. 

In  winter  they  moderate  the  cold,  and  in  summer  reduce  the  heat 
and  lessen  the  danger  from  storms.  Birds  nesting  in  the  woods 
protect  many  valuable  plants  which  otherwise  might  be  destroyed 
by  insects. 

Forests  have  great  commercial  importance.  Pyrogallic  and 
other  acids  are  obtained  from  trees,  as  are  tar,  creosote,  resin,  tur- 
pentine, and  many  useful  oils.  The  making  of  maple  sirup  and 
sugar  forms  a  profitable  industry  in  several  states. 

The  Forest  Regions  of  the  United  States.  —  The  combined  area 
of  all  the  forests  in  the  United  States,  exclusive  of  Alaska,  is  about 
500,000,000  acres.     This  seemingly  immense  area  is  rapidly  de- 


110 


OUR  FORESTS 


creasing  in  acreage  and  in  quality,  thanks  to  the  demands  of  an 
increasing  population,  a  woeful  ignorance  on  the  part  of  the  owners 
of  the  land,  and  wastefulness  on  the  part  of  cutters  and  users  alike. 
A  glance  at  the  map  on  page  109  shows  -the  distribution  of 
our  principal  forests.  Washington  ranks  first  in  the  produc- 
tion of  lumber.  Here  the  great  Douglas  fir,  one  of  the  "  ever- 
greens," forms  the  chief  source  of  supply.  In  the  Southern  states, 
especially  Louisiana  and  Mississippi,  yellow  pine  and  cypress  are 
the  trees  most  lumbered. 

Which  states  produce  the  most  hardwoods  ?  From  which  states 
do  we  get  most  of  our  yellow  pine,  spruce,  red  fir,  redwood? 
Where  are  the  heaviest  forests  of  the  United  States  ? 

Uses  of  Wood.  —  Even  in  this  day  of  coal,  wood  is  still  by  far 
the  most  used  fuel.     It  is  useful   in  building.     It  outlasts  iron 

under  water,  in  addition  to 
being  durable  and  light. 
It  is  cheap  and,  with  care 
of  the  forests,  inexhaust- 
ible, while  our  mineral 
wealth  may  some  day  be 
used  up.  Distilled  wood 
gives  wood  alcohol.  Par- 
tially burned  wood  is  char- 
coal. In  our  forests  much 
of  the  soft  wood  (the  cone- 
bearing  trees,  spruce,  bal- 
sam, hemlock,  and  pine), 
and  poplars,  aspens,  basswood,  with  some  other  species,  make  paper 
pulp.  The  daily  newspaper  and  cheap  books  are  responsible  for  in- 
roads on  our  forests  which  cannot  well  be  repaired.  It  is  not  nec- 
essary to  take  the  largest  trees  to  make  pulp  wood.  Hence  many 
young  trees  of  not  more  than  six  inches  in  diameter  are  sacrificed. 
Of  the  hundreds  of  species  of  trees  in  our  forests,  the  conifers  are 
probably  most  sought  after  for  lumber.  Pine,  especially,  is  prob- 
ably used  more  extensively  than  any  other  wood.  It  is  used  in 
all  heavy  construction  work,  frames  of  houses,  bridges,  masts, 
spars  and  timber  of  ships,  floors,  railway  ties,  and  many  other 


Transportation  of  ]  umber  in  the  West. 
A  logging  train. 


OUR  FORESTS 


HI 


purposes.     Cedar  is  used  for  shingles,  cabinetwork,  lead  pencils, 
etc. ;  hemlock  and  spruce  for  heavy  timbers  and,  as  we  have  seen, 


Transportation  of  lumber  in  the  East.     Logs  are  mostly  floated  down  rivers 

to  the  mills. 

for  paper  pulp.  Another  use  for  our  lumber,  especially  odds  and 
ends  of  all  kinds,  is  in  the  packing-box  industry.  It  is  estimated 
that  nearly  50  per  cent  of  all  lumber  cut  ultimately  finds  its  way 
into  the  construction  of  boxes. 
Hemlock  bark  is  used  for  tanning. 
The  hard  woods  —  ash,  bass- 
wood,  beech,  birch,  cherry,  chest- 
nut, elm,  maple,  oak,  and  walnut 
— are  used  largely  for  the  '^trim'^ 
of  our  houses,  for  manufacture  of 
furniture,  wagon  or  car  work,  and 
endless  other  purposes. 


a 


Methods    of    cutting    Timber.  —  A    Diagrams     of     sections     of      timber. 

glance  at  the  diagram  of  the  sections       ^'  ^/^f  %^*^°^:  .^'  ^^^f  jl' a''r.^''T 
„    .     .  gential.     (From  Pmchot,  U.  S.  Dept. 

of  timber  shows  us  that  a  tree  may  be       of  Agriculture.) 

cut   radiallj^  through   the  middle  of 

the  trunk  or  tangentially  to  the  middle  portion.     Most  lumber  is  cut 

tangentially.     In  wood  cut  in  this  manner  the  yearly  rings  take  a  more 

or  less  irregular  course.     The  grain  in  wood  is  caused  by  the  fibers  not 


112 


OUR  FORESTS 


Section  of  a  tree  trunk 
showing  knot. 


taking  straight  lines  in  their  course  in  the  tree  trunk.  In  many  cases  the 
fibers  of  the  wood  take  a  spiral  course  up  the  trunk,  or  they  may  wave 
outward  to  form  little  projections.     Boards  cut  out  of  such  a  piece  of 

wood  will  show  the  effect  seen  in  many  of  the  school 
desks,  where  the  annual  rings  appear  to  form  eUip- 
tical  markings.  Quite  a  difference  in  color  and 
structure  is  often  seen  between  the  heartwood, 
composed  of  the  dead  walls  of  cells  occupying  the 
central  part  of  the  tree  trunk,  and  the  sapwood, 
the  living  part  of  the  stem. 

Knots.  —  Knots,  as  can  be  seen  from  the  dia- 
gram, are  branches  which  at  one  time  started  in 
their  outward  growth  and  were  for  some  reason 
killed.     Later,  the  tree,  continuing  in  its  outward 
growth,  surrounded  them  and   covered  them  up. 
A  dead  limb  should  be  pruned  before  such  growth  occurs.     The  markings 
in  bird's-eye  maple  are  caused  by  buds  which  have  not  developed,  and 
have  been  overgrown  with  the  wood  of  the  tree. 

Destruction  of  the  Forest.  —  By  Waste  in  Cutting.  —  Man  is 
responsible  for  the  destruction  of  one  of  this  nation's  most  valuable 
assets.!  This  is  primarily  due  to  wrong  and  wasteful  lumbering. 
Hundreds  of  thousands  of  dollars'  worth  of  lumber  is  left  to  rot 
annually  because  the  lumbermen  do  not  cut  the  trees  close  enough 
to  the  ground.  Or  because  through  careless  felling  of  trees  many 
other  smaller  trees  are  injured.  There  is  great  waste  in  the  mills. 
In  fact,  man  wastes  in  every  step  from  the  forest  to  the  finished 
product. 

By  Fire.  —  Indirectly,  man  is  responsible  for  fire,  one  of  the 
greatest  enemies  of  the  forest.  Most  of  the  great  forest  fires  of 
recent  years,  the  losses  from  which  total  in  the  hundreds  of  mil- 
lions, have  been  due  either  to  railroads  or  to  carelessness  in  making 
fires  in  the  woods.  It  is  estimated  that  in  forest  lands  traversed 
by  railroads  from  25  per  cent  to  90  per  cent  of  the  fires  are  caused 
by  coal-burning  locomotives.  For  this  reason  laws  have  been  made 
in  New  York  State  requiring  locomotives  passing  through  the 
Adirondack  forest  preserve  to  burn  oil  instead  of  coal.  This 
has  resulted  in  a  considerable  reduction  in  the  number  of  fires.  In 
addition  to  the  loss  in  timber,  the  fires  often  burn  out  the  organic 


OUR  FORESTS 


113 


matter  in  the  soil  (the  ''  duff  ")  forming  the  forest  floor,  thus  pre- 
venting the  growth  of  forest  there  for  many  years  to  come.  In 
New  York  and  other  states  fires  are  fought  by  an  organized  corps 


A  forest  in  the  far  west  totally  destroyed  by  fire  and  wasteful  lumbering. 

of  fire. wardens,  whose  duty  it  is  to  watch  the  forest  and  to  fight 
forest  fires. 

Other  Enemies.  —  Other  enemies  of  the  forest  are  numerous 
fungus  plants,  insect  parasites  which  bore  into  the  wood  or  destroy 
the  leaves,  and  grazing  animals,  particularly  sheep.  Wind  and 
snow  also  annually  kill  many  trees. 

Forestry.  —  In  some  parts  of  central  Europe,  the  value  of  the 
forests  was  seen  as  early  as  the  year  1300  a.d.,  and  many  towns 
consequently  bought  up  the  surrounding  forests.  The  city  of 
Zurich  has  owned  forests  in  its  vicinity  for  at  least  600  years  and 
has  found  them  a  profitable  investment.  In  this  country  only 
recently  has  the  importance  of  preserving  and  caring  for  our 
forests  been  noted  by  our  government.  Now,  however,  we  have  a 
Forest  Survey  of  the  Department  of  Agriculture  and  numerous 
state  and  university  schools  of  forestry  which  are  rapidly  teach- 

HUNTER,  CIV.  BI.  —  8 


114 


OUR  FORESTS 


The  forest  primeval.  Trees  are  killing 
each  other  in  the  struggle  for  light 
and  air. 


ing  the  people  of  this  country  the 
best  methods  for  the  preserva- 
tion of  our  forests.  The  Federal 
government  has  set  aside  a  num- 
ber of  tracts  of  mountain  forest 
in  some  of  the  Western  states, 
making  a  total  area  of  over 
167,000,000  acres.  New  York 
has  established  for  the  same  pur- 
pose the  Adirondack  Park,  with 
nearly  1,500,000  acres  of  timber- 
land.  Pennsylvania  has  one  of 
700,000  acres,  and  many  other 
states  have  followed  their  ex- 
ample. 

Methods  for  Keeping  and  Pro- 
tecting the  Forests.  —  Forests 
should  be  kept  thinned.  Too  many  trees  are  as  bad  as  too  few. 
They  struggle  with  one  another  for  foothold  and  light,  which  only 
a  few  can  enjoy.  In  cutting 
the  forest,  it  should  be  con- 
sidered as  a  harvest.  The 
oldest  trees  are  the  [^  ripe 
grain,"  the  younger  trees 
being  left  to  grow  to  matur- 
ity. Several  methods  of  re- 
newing the  forest  are  in  use 
in  this  country.  (1)  Trees 
may  be  cut  down  and  young 
ones  allowed  to  sprout  from 
cut  stumps.  This  is  called 
coppice  growth.  This  growth 
is  well  seen  in  parts  of  New 
Jersey.     (2)  Areas  or  strips 

may  be  cut  out  so  that  seeds      A  German  beech  forest.     The  trees  are  kept 
from    Tipio-hhnrine-    trpp^    arp         thinned  out  so  as  to  allow  the  young  trees 

irom  neignoormg  irees    are        ^^  ^^^  ^  ^^^^^     Contrast  this  with  the 
carried   there   to  start  new       picture  above. 


OUR  FORESTS 


115 


growth.  (3)  Forests  may  be  artificially 
planted.  Two  seedlings  planted  for  every 
tree  cut  is  a  rule  followed  in  Europe.  (4) 
The  most  economical  method  is  that  shown 
in  the  lower  picture  on  page  114,  where  the 
largest  trees  are  thinned  out  over  a  large 
area  so  ^s  to  make  room  for  the  younger 
ones  to  grow  up.  The  greatest  dangers 
to  the  forests  are  from  fire  and  from  care- 
less cutting,  and  these  dangers  may  be 
kept  in  check  by  the  efficient  work  of  our 
national  and  state  foresters. 

A  City's  Need  for  Trees.  — The  city  of 
Paris,  well  known  as  one  of  the  most 
beautiful  of  European  capitals,  spends 
over  $100,000  annually  in  caring  for  and 
replacing  some  of  the  90,000  trees  owned 
by  the  city.  All  over  the  United  States 
the  city  governments  are  beginning  to 
realize  what  European  cities  have  long 
known,  that  trees  are  of  great  value  to  a 

city.  They  are  now  following  the  example  of  European  cities  by 
planting  trees  and  by  protecting  the  trees  after  they  are  planted. 
Thousands  of  city  trees  are  annually  killed  by  horses  which 
gnaw  the  bark.  This  may  be  prevented  by  proper  protection  of 
the  trunk  by  means  of  screens  or  wire  guards.  Chicago  has 
appointed  a  city  forester,  who  has  given  the  following  excellent 
reasons  why  trees  should  be  planted  in  the  city :  — 

(1)  Trees  are  beautiful  in  form  and  color,  inspiring  a  constant  appreci- 
ation of  nature. 

(2)  Trees  enhance  the  beauty  of  architecture. 

(3)  Trees  create  sentiment,  love  of  country,  state,  city,  and  home. 

(4)  Trees  have  an  educational  influence  upon    citizens   of  all  ages, 
especially  children. 

(5)  Trees  encourage  outdoor  life. 

(6)  Trees  purify  the  air. 

(7)  Trees  cool  the  air  in  summer  and  radiate  warmth  in  winter. 

(8)  Trees  improve  climate  and  conserve  soil  and  moisture. 


We  must  protect  our  city 
trees.  This  tree  was 
badly  wounded  by  be- 
ing gnawed  by  a  horse. 


116  OUR  FORESTS 

(9)  Trees  furnish  resting  places  and  shelter  for  birds. 

(10)  Trees 'increase  the  value  of  real  estate. 

(11)  Trees  protect  the  pavement  from  the  heat  of  the  sun. 

(12)  Trees  counteract  adverse  conditions  of  city  life. 

Let  us  all  try  to  make  Arbor  Day  what  it  should  be,  a  day  for 
caring  for  and  planting  trees,  for  thus  we  may  preserve  this  most 
important  heritage  of  our  nation. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Mayne  and  Hatch,  High  School  Agriculture.     American  Book  Company. 
Murrill,  Shade  Trees,  Bui.  205,  Cornell  University  Agricultural  Experiment  Station. 
Pinchot,  A  Primer  of  Forestry,  Division  of   Forestry,  U.  S.  Department  of  Agri- 
culture. 

ADVANCED 

Apgar,  Trees  of  the  United  States,  Chaps.  II,  V,  VI.     American  Book  Company. 
Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Part  I  and  Vol.  II.     American 

Book  Company. 
Goebel,  Organography  of  Plants,  Part  V.     Clarendon  Press. 
Strasburger,  Noll,  Schenck,  and  Karston,  A  Textbook  of  Botany.     The  Macmillan 

Company. 
Ward,  Timber  and  Some  of  its  Diseases.     The  Macmillan  Company. 
Yearbook,  U.S.  Department  of  Agriculture,  Division  of  Forestry,  Buls.  7,  10,  13, 

16,  17,  18,  20,  26,  27. 


X.     THE   ECONOMIC    RELATION    OF    GREEN    PLANTS 

TO   MAN 

Problems.  — How  green  plants  are  useful  to  man. 
{a)  As  food. 

(b)  For  clothing. 

(c)  Other  uses. 

How  green  plants  are  harmful  to  man. 

Suggested  Laboratory  Work 

If  a  commercial  museum  is  available,  a  trip  should  be  planned  to  work 
over  the  topics  in  this  chapter.  The  school  collection  may  well  include 
most  of  the  examples  mentioned,  both  of  useful  and  harmful  plants. 

A  study  of  weeds  and  poisonous  plants  should  be  taken  up  in  actual 
laboratory  work,  either  by  collection  and  identification  or  by  demon- 
stration. 

Green  Plants  have  a  "  Dollar  and  Cents  "  Value.  —  To  the  girl 
or  boy  living  in  the  city  green  plants  seem  to  have  little  direct 
value.  Although  we  see  vegetables  for  sale  in  stores  and  we  know 
that  fruits  have  a  money  value,  we  are  apt  to  forget  that  the  wealth 
of  our  nation  depends  more  upon  its  crops  than  it  does  on  its 
manufactories  and  business  houses.  The  economic  or  "  dollars 
and  cents  "  value  of  plants  is  enormous  and  far  too  great  for  us 
to  comprehend  in  terms  of  figures. 

We  have  already  seen  some  of  the  uses  to  mankind  of  the 
products  of  the  forest ;  let  us  now  consider  some  other  plant 
products. 

Leaves  as  Food.  —  Grazing  animals  feed  almost  entirely  on 
tender  shoots  or  leaves,  blades  of  grass,  and  other  herbage. 
Certain  leaves  and  buds  are  used  by  man  as  food.  Lettuce, 
beet  tops,  kale,  spinach,  broccoli,  are  examples.  A  cabbage 
head  is  nothing  but  a  big  bud  which  has  been  cultivated  by 

117 


118    ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS 

man.     An  onion  is  a  compact  budlike  mass  of  thickened  leaves 
wriich  contain  stored  food. 


Cabbage 


Onions 
Leaves  used  as  food. 


Lettuce 


Stems  as  Food.  —  A  city  child  would,  if  asked  to  name  some 
stem  used  as  food,  probably  mention  asparagus.     We  sometimes 

forget  that  one  of  our 
greatest  necessities,  cane 
sugar,  comes  from  the 
stem  of  sugar  cane.  Over 
seventy  pounds  of  sugar 
is  used  each  year  by  every 
person  in  the  United 
States.  To  supply  the 
growing  demand  beets  are 
now  being  raised  for  their 
sugar  in  many  parts  of 
the  world,  so  that  nearly 
half  the  total  supply  of 
sugar  comes  from  this 
source.  Maple  sugar  is 
a  well-known  commodity 
which  is  obtained  by  boil- 
ing the  sap  of  sugar  maple  until  it  crystallizes.  Over  16,000  tons 
of  maple  sugar  is  obtained  every  spring,  Vermont  producing  about 
40  per  cent  of  the  total  output.     The  sago  palm  is  another  stem 


Celery  Kohl-rabi  Potato 

Stems  used  as  food. 


Sugar  cane 


ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS     119 

which  supports  the  life  of  many  natives  in  Africa.  Another  stem, 
living  underground,  forms  one  of  man's  staple  articles  of  diet. 
This  is  the  potato. 

Roots  as  Food.  —  Roots  which  store  food  for  plants  form  im- 
portant parts  of  man's  vegetable  diet.  Beets,  radishes,  carrots, 
parsnips,  sweet  potatoes,  and  many  others  might  be  mentioned. 

The  following  table  shows  the  proportion  of  foods  in  some  of 
the  commoner  roots  and  stems  :  — 


Potato  .  . 

Carrot  .  . 

Parsnip  .  . 

Turnip  .  . 

Onion  .  .  . 
Sweet  potato 

Beet     .  .  . 


Water 

Proteins 

Carbo- 
hydrates 

Fat 

75 

1.2 

18 

0.3 

89 

0.5 

5 

0.2 

81 

1.2 

8.7 

1.5 

92.8 

0.5 

4. 

0.1 

91 

1.5 

4.8 

0.2 

74 

1.5 

20.2 

0.1 

82.2 

0.4 

13.4 

0.1 

Mineral 
Matter 


1.0 
1.0 
1.0 
0.8 
0.5 
1.5 
0.9 


Fruits  and  Seeds  as  Foods.  —  Our  cereal  crops,  corn,  wheat, 
etc.,  have  played  a  very  great  part  in  the  civilization  of  man  and 
are  now  of  so  much  importance  to  him  as  food  products  that  bread 


Wheat 


Nuts  Pear 

Seeds  and  fruits  used  for  food. 


Melon 


made  from  flour  from  the  wheat  has  been  called  the  "  staff  of  life." 
Our  grains  are  the  cultivated  progeny  of  wild  grasses.     Domesti- 


120    ECONOMIC   IMPORTANCE  OF  GREEN  PLANTS 

cation  of  plants  and  animals  marks  epochs  in  the  advance  of  civili- 
zation. The  man  of  the  stone  age  hunted  wild  beasts  for  food, 
and  lived  like  one  of  them  in  a  cave  or  wherever  he  happened  to 
be ;  he  was  a  nomad,  a  wanderer,  with  no  fixed  home.  He  may 
have  discovered  that  wild  roots  or  grains  were  good  to  eat ;  per- 
haps he  stored  some  away  for  future  use.  Then  came  the  idea  of 
growing  things  at  home  instead  of  digging  or  gathering  the  wild 
fruits  from  the  forest  and  plain.  The  tribes  which  first  cultivated 
the  soil  made  a  great  step  in  advance,  for  they  had  as  a  result  a 
fixed  place  for  habitation.  The  cultivation  of  grains  and  cereals 
gave  them  a  store  of  food  which  could  be  used  at  times  when  other 
food  was  scarce.  The  word  "  cereal  "  (derived  from  Ceres,  the 
Roman  Goddess  of  Agriculture)  shows  the  importance  of  this  crop 
to  Roman  civilization.  From  earliest  times  the  growing  of  grain 
and  the  progress  of  civilization  have  gone  hand  in  hand.  As 
nations  have  advanced  in  power,  their  dependence  upon  the  cereal 
crops  has  been  greater  and  greater. 

^'  Indian  corn,"  says  John  Fiske,  in  The  Discovery  of  America, 
''  has  played  a  most  important  part  in  the  history  of  the  New 
World.  It  could  be  planted  without  clearing  or  plowing  the  soil. 
There  was  no  need  of  threshing  or  winnowing.  Sown  in  tilled  land, 
it  yields  more  than  twice  as  much  food  per  acre  as  any  other  kind 
of  grain.  This  was  of  incalculable  advantage  to  the  English 
settlers  in  New  England,  who  would  have  found  it  much  harder 
to  gain  a  secure  foothold  upon  the  soil  if  they  had  had  to  begin  by 
preparing  it  for  wheat  or  rye." 

To-day,  in  spite  of  the  great  wealth  which  comes  from  our 
mineral  resources,  live  stock,  and  manufactured  products,  the 
surest  index  of  our  country's  prosperity  is  the  size  of  the  corn 
and  wheat  crop.  According  to  the  last  census,  the  amount  of 
capital  invested  in  agriculture  was  over  $20,000,000,000,  while 
that  invested  in  manufacture  was  less  than  one  half  that  amount. 

Corn.  —  About  three  billion  bushels  of  corn  were  raised  in  the 
United  States  during  the  year  1910.  This  figure  is  so  enormous 
that  it  has  but  little  meaning  to  us.  In  the  past  half  century 
our  corn  crop  has  increased  over  350  per  cent.  Illinois  and  Iowa 
are  the  greatest  corn-producing  states,  each  having  a  yearly  record 


ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS     121 


of  over  four  hundred  million  bushels.     The  figure  on  this  page 
shows  the  principal  corn-producing  areas  in  the  United  States. 

Indian  com  is  put  to  many  uses.  It  is  a  valuable  food,  it  con- 
tains a  large  proportion  of  starch,  from  which  glucose  (grape  sugar) 
and  alcohol  are  made.  Machine  oil  and  soap  are  made  from  it. 
The  leaves  and  stalk  are  an  excellent  fodder ;  they  can  be  made 
into  paper  and  packing  material.     Mattresses  can  be  stuffed  with 


"^^ 


/  ^"L 


CORN 

640  to  3200  bushels  per  saaare  mile 
oyer  3200        „  „         »       » 


Indian  Corn  Production — Percentage 


10 
1                    I 

20 

30 

40 

50 

60                     70 

80 

9.0                      , 

w///////////m\ 

V////WM 

v/mm 

^W//////A 

V//MW/M 

,  .w/mm 

Illinois 


Iowa 


Mo. 


Neb.       Ind.     Kan.   Tex.  Ohio 


Rest  of  United  States 


the  husks.  The  pith  is  used  as  a  protective  belt  placed  below  the 
water  line  of  our  huge  battleships.  Corn  cobs  are  used  for  fuel, 
one  hundred  bushels  having  the  fuel  value  of  a  ton  of  coal. 

Wheat.  —  Wheat  is  the  crop  of  next  greatest  importance  in  size. 
Nearly  seven  hundred  millions  of  bushels  were  raised  in  this 
country  in  1910,  representing  a  total  money  value  of  over  $700,- 
000,000.  Seventy-two  per  cent  of  all  the  wheat  raised  comes  from 
the  North  Central  states  and  California.  About  three  fourths  of 
the  wheat  crop  is  exported,  nearly  one  half  of  it  to  Great  Britain, 
thus  indirectly  giving  employment  to  thousands  of  people  on  rail- 
ways and  steamships.    Wheat  has  its  chief  use  in  its  manufacture 


122    ECONOMIC   IMPORTANCE  OF   GREEN   PLANTS 


into  flour.     The  germ,  oi  young  wheat  plartt,  is  sifted  out  during 
this  process  and  made  into  breakfast  foods.     Flour  making  forms 


U/  ^ 


v,^ 


/60  to  640  bushe/s  per  sauare  mile  \ 

over   640 


\W' 


10 

I 


Wheat  Crop  in  United  States  — Percentage  Source 

20  30  4.0  50 60 


JR. 


80 
_1 


90 


J 


± 


J. 


Minnesota       Kansas        N.Dak.      Neb.     Ind.    S.D.  Wash.  O.    Mo. 


Other  States 


the  chief  industry  of  Minneapolis,  Minnesota,  and  of  several  oltier 
large  and  wealthy  cities  in  this  country. 

Other  Grains.  —  Of  the  other  grain  and  cereals  raised  in  this 
country,  oats  are  the  most  important  crop,  over  one  billion  bushels 
having  been  produced  in  1910.  Barley  is  another  grain,  a  staple 
of  some  of  the  northern  countries  of  Europe  and  Asia.  In  this 
country,  it  is  largely  used  in  making  malt  for  the  manufacture  of 
beer.  Rye  is  the  most  important  cereal  crop  of  northern  Europe, 
Russia,  Germany,  and  Austro-Hungary  producing  over  50  per 
cent  of  the  world's  supply.  One  of  the  most  important  grain  crops 
for  the  world  (although  relatively  unimportant  in  the  United 
States)  is  rice.  The  fruit  of  this  grasslike  plant,  after  thrashing, 
screening,  and  milling,  forms  the  principal  food  of  one  third  of  the 
human  race.  Moreover,  its  stems  furnish  straw,  its  husks  make 
a  bran  used  as  food  for  cattle,  and  the  grain^  when  fermented  and 
distilled,  yields  alcohoU 


ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS    123 


A  field  of  rice,  showing  tlie  conditions  of  culture. 


Garden  Fruits.  —  Green  plants  and  especially  vegetables  have 
come  to  play  an  important  part  in  the  dietary  of  man.  The 
diseases  known  as  scurvy  and  beri-beri,  the  latter  the  curse  of  the 
far  Eastern  navies,  have  been  largely  prevented  hy  adding  vege- 
tables and  fruit  juices  to  the  dietary  of  the  sailors.  People  in 
this  country  are  beginning  to  find  that  more  vegetables  and  less 
meat  are  better  than  the  meat  diet  so  often  used.  Market  gar- 
dening forms  the  lucrative  business  of  many  thousands  of  people 
near  our  great  cities.  Some  of  the  more  important  fruits  are 
squash,  cucumbers,  pumpkins,  melons,  tomatoes,  peppers,  straw- 
berries, raspberries,  and  blackberries.  The  latter  fruits  bring  in 
an  annual  income  of  $25,000,000  to  our  market  gardeners.  Beans 
and  peas  are  important  as  foods  because  of  their  relatively  large 


124    ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS 


amount  of  protein.     Canning  green  corn,  peas,  beans,  and  toma- 
toes has  become  an  important  industry. 

Orchard  and  Other  Fruits.  —  In  the  United  States  over  one 
hundred  and  seventy-five  million  bushels  of  apples  are  grown  every 
year.  Pears,  plums,  apricots,  peaches,  and  nectarines  also  form 
large  orchards,  especially  in  California.     Nuts  form  one  of  our 

important  articles  of  food, 
largely  because  of  the  large 
amount  of  protein  contained 
in  them. 

The  grape  crop  of  the 
world  is  commercially  valu- 
able, because  of  the  raisins 
and  wine  produced.  The 
culture  of  lemons,  oranges, 
and  grapefruit  has  come 
in  recent  years  to  give  a 
living  to  many  people  in 
this  country  as  well  as  in 
other  parts  of  the  world. 
Figs,  olives,  and  dates  are 
staple  foods  in  the  Mediter- 
ranean countries  and  are 
sources  of  wealth  to  the 
people  there,  as  are  coco- 
nuts, bananas,  and  many 
other  fruits  in  tropical 
countries. 
Beverages  and  Condiments. — The  coffee  and  cacao  beans,  and 
leaves  of  the  tea  plant,  products  of  tropical  regions,  form  the  basis 
of  very  important  beverages  of  civilized  man.  Pepper,  black  and 
red,  mustard,  allspice,  nutmegs,  cloves,  and  vanilla  are  all  products 
manufactured  from  various  fruits  or  seeds  of  tropical  plants. 

Alcoholic  liquors  are  produced  from  various  plants  in  different 
parts  of  the  world,  the  dried  fruit  of  the  hop  vine  being  an 
important  product  of  New  York  State  used  in  the  making  of 
beer. 


Picking  apples,  an  important  crop  in  some 
parts  of  the  United  States. 


ECONOMIC   IMPORTANCE  OF   GREEN   PLANTS     125 

Raw  Materials.  —  Besides  use  as  food,  green  plants  have  many- 
other  uses.  Many  of  our  city  industries  would  not  be  in  existence, 
were  it  not  for  certain  plant  products  which  furnish  the  raw  ma- 
terials for  many  manufacturing  industries.  Many  cities  of  the 
east  and  south,  for  example,  depend  upon  cotton  to  give  employ- 
ment to  thousands  of  factory  hands. 

Cotton.  —  Of  our  native  plant  products  cotton  is  probably  of 
the  most  importance  to  the  outside  world.  Over  eleven  million 
bales  of  five  hundred  pounds  each  are  raised  annually. 


COTTON 

^3  /to  BO  bales  persaaare  mile 
\over£0  . 


Cotton  Crop  in  United  States  —  Percentage  Source 


'1.0 


20 


I^MJM^^^dmm^J^mi^ 


3.0 


40 
I 


5.0 


60 
_i_ 


7.0 


80 

_l 


90 


WWM        ML 


Texas 


Georgia 


Miss. 


Alabama        S.Car. 


Ark.       Okla.     N.C.  La.  Otli. 
Sta. 


[ir.'.^iy.vy//'/'/'/'^-''- 


Cotton  Crop  in  United  States  —  Percentage  Consumption 

10  20  30  M  50  60  70  80  90 


V^//^,i//^^/\       ' ■ I 


r  ] 


J± 


United  States 
North  South 


Great  Britain  &  Ireland 


Germany  France     It.     Rest  ol 

World 


The  cotton  plant  thrives  in  warm  regions.  Its  commercial 
importance  is  gained  because  the  seeds  of  the  fruit  have  long  fila- 
ments attached  to  them.  Bunches  of  these  filaments,  after  treat- 
ment, are  easily  twisted  into  threads  from  which  are  manufactured 
cotton  cloth,  muslin,  calico,  and  cambric.     In  addition  to  the 


126    ECONOMIC   IMPORTANCE  OF  GREEN   PLANTS 

fiber,  cottonseed  oil,  a  substitute  for  olive  oil,  is  made  from  the 
seeds,  and  the  refuse  remaining  makes  an  excellent  cattle  fodder. 
Cotton  Boll  Weevil.  —  The  cotton  crop  of  the  United  States  has 
rather  recently  been  threatened  with  destruction  by  a  beetle  called 
the  cotton  boll  weevil.     This  insect,  which  bores  into  the  young 


GULF      OF      ME 


c  o 


Map  showing  the  spread  of  the  cotton  boll  weevil.     It  was  introduced  from  Mexico 
about  1894.     What  proportion  of  the  cotton  raising  belt  was  infected  in  1908  ? 


pod  of  the  cotton,  develops  there,  stunting  the  growth  of  the  fruit 
to  such  an  extent  that  seeds  are  not  produced.  The  loss  in  Texas 
alone  is  estimated  at  over  $10,000,000  a  year.  The  boll  weevil, 
because  of  the  protection  offered  by  the  cotton  boll,  is  very  diffi- 
cult to  exterminate.  The  weevils  are  destroyed  by  birds,  the 
infected  bolls  and  stalks  are  burnt,  millions  are  killed  each  winter 


ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS     127 

by  cold,  other  insects  prey  on  them,  but  at  the  present  time  they 
are  one  of  the  greatest  pests  the  south  knows. 

The  control  of  this  pest  seems  to  depend  upon  early  planting  so 
that  the  crop  has  an  opportunity  to  ripen  before  the  insects  in  the 
boll  grow  large  enough  to  do  harm.     Ultimately  the  boll  weevil 


Mexican  cotton  boll  weevil.     Much  enlarged,  above;  natural 

size,  below.     (Herrick.) 

may  do  more  good  than  harm  by  bringing  into  the  market  a  type 
of  cotton  plant  that  ripens  very  early. 

Vegetable  Fibers.  —  Among  the  most  important  are  Manila 
hemp;  which  comes  from  the  leaf-stalks  of  a  plant  of  the  banana 
family  and  true  hemp,  which  is  the  bast  or  woody  fiber  of  a  plant 
cultivated  in  most  warm  parts  of  the  earth.  Flax  is  also  an  im- 
portant fiber  plant,  grown  largely  in  Russia  and  other  parts  of 
Europe  (see  picture  on  next  page) .  From  the  bast  fibers  of  the 
stem  of  this  herb  linen  cloth  is  made. 

Vegetable  Oils.  —  Some  of  the  same  plants  which  give  fiber 
also  produce  oil.  Cotton  seed  oil  pressed  from  the  seeds,  linseed 
oil  from  the  seeds  of  the  flax  plant,  and  coconut  oil  (the  covering 
of  the  nut  here  producing  the  fiber)  are  examples. 

Some  Harmful  Green  Plants.  —  We  have  seen  that  on  the  whole 
green  plants  are  useful  to  man.     There  are,  however,  some  that 


128    ECONOMIC  IMPORTANCE  OF  GREEN   PLANTS 


-.•DJiSP-^- 


WW" 


are  harmful.  For  example,  the 
poison  ivy  is  extremely  poison- 
ous to  touch.  The  poison  ivy 
is  a  climbing  plant  which  at- 
taches itself  to  the  trees  or 
walls  by  means  of  tiny  air 
roots  which  grow  out  from  the 
stem.  It  is  distinguished  from 
its  harmless  climbing  neighbor, 
the  Virginia  Creeper,  by  the 
fact  that  its  leaves  are  notched 
in  threes  instead  of  jives.  Every 
boy  and  girl  should  know 
poison  ivy. 

Numerous  other  poisonous 
common  plants  are  found,  but 
one  other  deserves  special 
notice  because  of  its  presence 
in  vacant  city  lots.     The  Jim- 


Flax  grown  for  fiber. 

son  Weed  {Datura)  is  a  bushy  plant, 
from  two  to  five  feet  high,  bearing 
large  leaves.  It  has  white  or  pur- 
plish flowers,  and  later  bears  a  four- 
valved  seed  pod  containing  several 
hundred  seeds.  These  plants  con- 
tain a  powerful  poison,  and  people 
are  often  made  seriously  ill  by 
eating  the  roots  or  other  parts  by 
mistake. 

Weeds.  —  From     the     economic 
standpoint  the  green  plants  which 


Poison  ivy,  a  climbing  plant  which 
is  poisonous  to  touch.  Notice  the 
leaves  in  threes. 


ECONOMIC  IMPORTANCE  OF  GREEN  PLANTS     129 

do  the  greatest  damage  are  weeds.  Those  plants  which  provide 
best  for  their  young  are  usually  the  most  successful  in  life's 
race.  Plants  which  combine  with  the  ability  to  scatter  many 
seeds  over  a  wide  territory  the  additional  characteristics  of  rapid 
growth,  resistance  to  dangers  of  extreme  cold  or  heat,  attacks  of 
enemies,  inedibility,  and  peculiar  adaptations  to  cross-pollina- 
tion or  self-pollination,  are  usually  spoken  of  as  weeds.  They 
flourish  in  the  sterile  soil  of  the  roadside  and  in  the  fertile  soil  of 
the  garden.  By  means  of  rapid  growth  they  kill  other  plants  of 
slower  growth  by  usurping  their  territory.  Slow-growing  plants 
are  thus  actually  exterminated.  Many  of  our  common  weeds 
have  been  introduced  from  other  countries  and  have,  through 
their  numerous  adaptations,  driven  out  other  plants  which  stood 
in  their  way.  Such  is  the  Russian  Thistle.  A  single  plant  of 
this  kind  will  give  rise  to  over  20,000  seeds.  First  introduced  from 
Russia  in  1873,  it  spread  so  rapidly  that  in  twenty  years  it  had 
appeared  as  a  common  weed  over  an  area  of  some  twenty-five 
thousand  square  miles.     It  is  now  one  of  the  greatest  pests  in  our 

Northwest. 

» 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Gannet,  Commercial  Geography.     American  Book  Company. 

Sargent,  Plants  and  their  Uses.     Henry  Holt  and  Company. 

Toothaker,  Commercial  Raw  Materials.     Ginn  and  Company. 

U.  S.  Dept.  of  Agriculture,  Farmers'  Bulletin  86,  Thirty  Poisonous  Plants  of  the 

United  States,  V.  K.  Chestnut.      Bulletin  17.      Two  Hundred  Weeds.  How  to 

Know  Them  and  How  to  Kill  Them,  L.  H.  Dewey. 

ADVANCED 

Bailey,  Cyclopedia  of  American  Agriculture.     The  Macmillan  Companv. 


HUNTER,  CIV.  BT. 9 


XI.     PLANTS  WITHOUT  CHLOROPHYLL  IN  THEIR 

RELATION   TO    MAN 

Problems,  —  (a)  How  molds  and  otlver  saprophytic  fungi  do 
harm  to  man. 

(5)    What  yeasts  do  for  mankind. 

(c)   A  study  of  bacteria  with  reference  to 

(1)   Conditions  favorable  and  unfavorable  to  growth. 
(^)  Their  relations  to  manhind. 

{8)  Some  methods  of  fighting  harmful  bacteria  and 
diseases  caused  by  them. 

Laboratory  Suggestions 

Field  work.  —  Presence  of  bracket  fungi  and  chestnut  canker. 

Home  experiment.  —  Conditions  favorable  to  growth  of  mold. 

Laboratory  demonstration.  —  Growth  of  mold,  structure,  drawing. 

Home  experiinent  or  laboratory  demonstration.  —  Conditions  unfavorable 
for  growth  of  molds. 

Demonstration.  —  Process  of  fermentation. 

Microscopic  demonstration.  —  Growing  yeast  cells.     Drawing. 

Home  experiment.  —  Conditions  favorable  for  growth  of  yeast. 

Home  experiment.  —  Conditions  favorable  for  growth  of  yeast  in  bread. 

Demonstration  and  experiment.  —  Where  bacteria  may  be  found. 

Demonstration.  —  Methods  of  growth  of  bacteria,  pure  cultures  and  col- 
onies shown. 

Demonstration.  —  Foods  preferred  by  bacteria. 

Demonstration.  —  Conditions  favorable  for  growth  of  bacteria. 

Demonstration.  —  Conditions  unfavorable  for  growth  of  bacteria. 

Demonstration  by  charts,  diagrams,  etc.  —  The  relation  of  bacteria  to 
disease  in  a  large  city. 

COLORLESS   PLANTS  ARE    USEFUL   AND   HARMFUL   TO   MAN 

The  Fungi.  —  We  have  found  that  green  plants  on  the  whole 
are  useful  to  mankind.  But  not  all  plants  are  green.  Most  of 
us  are  familiar  with  the  edible  mushroom  sold  in  the  markets  or 

130 


PLANTS  WITHOUT  CHLOROPHYLL 


131 


the  so-called  ''  toadstools "  found  in  parks  or  lawns.  These 
plants  contain  no  chlorophyll  and  hence  do  not  make  their  own 
food.  They  are  members  of  the  plant  group  called  fungi.  Such 
plants  are  almost  as  much  dependent  upon  the  green  plants  for 
food  as  are  animals.  But  the  fungi  require  for  the  most  part 
dead  organic  matter  for  their  food.  This  may  be  obtained  from 
decayed  vegetable  or  animal  material  in  soil,  from  the  bodies  of 
dead  plants  and  animals,  or  even  from  foods  prepared  for  man. 
Fungi  which  feed  upon  dead  organic  material  are  known  as  sap- 
rophytes.  Examples  are  the  mushrooms,  the  yeasts,  molds,  and 
some  bacteria,  of  which  more  will  be  learned  later. 

Some  Parasitic  Fungi.  —  Other  fungi  (and  we  will  find  this 
applies  to  some  animals  as  well)  prefer  living  plants  or  animals 
for  their  food.  Thus  a  tiny 
plant,  recently  introduced 
into  this  country,  known 
as  the  chestnut  canker,  is 
killing  our  chestnut  trees  by 
the  thousands  in  the  eastern 
part  of  the  United  States. 
It  produces  millions  of  tiny 
reproductive  cells  known  as 
spores;  these  spores,  blown 
about  by  the  wind,  light  on 
the  trees;  sprout,  and  send 
in  under  the  bark  a  thread- 
like structure  which  sucks 
in  the  food  circulating  in 
the  living  cells,  eventually 
causing  the  death  of  the 
tree.  A  plant  or  aniinal 
which  lives  at  the  expense  of 
another  living  plant  or  ani-    * 

mat  is  called  a  parasite.  The  chestnut  canker  is  a  dangerous 
parasite.  Later  we  shall  see  that  animal  and  plant  parasites  de- 
stroy yearly  crops  and  trees  valued  at  hundreds  of  millions  of 
dollars  and  cause  untold  misery  and  suffering  to  humanity. 


Chestnut  trees  in  a  New  York   City  park; 
killed  by  a  parasite,  the  chestnut  canker. 


132 


PLANTS   WITHOUT   CHLOROPHYLL 


Another  fungus  which  does  much  harm  to  the  few  trees  found 
in  large  towns  and  cities  is  the  shelf  or  bracket  fungus.  The  part 
of  the  body  visible  on  the  tree  looks  like  a  shelf  or  bracket,  hence 

the  name.  This  bracket  is  in 
reality  the  reproductive  part  of 
the  plant;  on  its  lower  surface 
are  formed  millions  of  little 
bodies  called  spores.  These 
spores  are  capable,  under  favor- 
able conditions,  of  reproducing 
new  plants.  The  true  body  of 
the  plant,  a  network  of  threads, 
is  found  under  the  bark.  This 
fungus  begins  its  life  as  a  spore 
in  some  part  of  the  tree  which 
has  become  diseased  or  broken. 
Once  established,  it  spreads 
rapidly.  There  is  no  remedy 
except  to  kill  the  tree  and  burn 
it,  so  as  to  destroy  the  spores. 
Many  fine  trees,  sound  except 
for  a  slight  bruise  or  other  in- 
jury, are  annually  infected  and  eventually  killed.  In  cities  thou- 
sands of  trees  become  infected  through  careless  hitching  of  horses 
so  that  the  horse  may  gnaw  the  tree,  thus  exposing  a  fresh  surface 
on  which  spores  may  obtain  lodgment  and  grow  (see  page  115). 

Suggestions  for  Field  Work.  —  A  field  trip  to  a  park  or  grove  near 
home  may  show  the  great  destruction  of  timber  by  this  means.  Count  the 
nimiber  of  perfect  trees  in  a  given  area.  Compare  it  with  the  number  of 
trees  attacked  by  the  fungus.  Does  the  fungus  appear  to  be  transmitted 
from  one  tree  to  another  near  at  hand  ?  In  how  many  instances  can  you 
discover  the  point  where  the  fungus  first  attacked  the  tree? 

Fungi  of  our  Homes.  —  But  not  all  fungi  are  wild.  Some  have 
become  introduced  into  our  homes  and  these  live  on  food  or  other 
materials.  These  plants  are  very  important  because  of  their  relation 
to  life  in  a  town  or  crowded  city.^ 


Shelf  fungi. 
(Photographed  by  W.  C.  Barbour.) 


'  Experiments  on  conditions  favorable  to  growth  of  mold  should  be  introduced  here. 


PLANTS   WITHOUT  CHLOROPHYLL 


133 


Bread  mold  ;  r,  rhizoids ;  s,  fruiting 
bodies  containing  spores. 


The  Growth  of  Bread  Mold.  —  If  a  piece  of  moist  bread  is 
exposed  to  the  air  of  the  schoolroom,  or  in  your  own  kitchen  for  a 
few  minutes  and  then  covered  with  a  glass  tumbler  and  kept  in  a 
warm  place,  in  a  day  or  two  a  fuzzy  whitish  growth  will  appear  on 
the  surface  of  the  bread.  This  growth  shortly  turns  black.  If  we 
now  examine  a  little  piece  of  the 
bread  with  a  lens  or  low-powered 
microscope,  we  find  a  tangled 
mass  of  threads  (the  mycelium) 
covering  the  surface  of  the  bread. 
From  this  mass  of  threads  pro- 
ject tiny  upright  stalks  bearing 
round  black  bodies,  the  fruit. 
Little  rootlike  structures  known 
as  rhizoids  dip  down  into  the 
bread,  and  absorb  food  for  its 
threadlike  body.  The  upright 
threads  with  the  balls  at  the  end  contain  many  tiny  bodies 
called  spores.  These  spores  have  been  formed  by  the  division  of 
the  protoplasm  making  up  the  fruiting  bodies  into  many  separate 
cells.  When  grown  under  favorable  conditions,  the  spores  will 
produce  more  mycelia,  which  in  turn  bear  fruiting  bodies. 

Physiology  of  the  Growth  of  Mold.  —  Molds,  in  order  to  grow 
rapidly,  need  oxygen,  moisture,  and  moderate  heat.  They  seem 
to  prefer  dark,  damp  places  where  there  is  not  a  free  circula- 
tion of  air,  for  if  the  bell  jar  is  removed  from  growing  mold 
for  even  a  short  time,  the  mold  wilts.  Too  great  or  very  little 
heat  will  prevent  growth  and  kill  everything  except  the  spores. 
They  obtain  their  food  from  the  material  on  which  they  live. 
This  they  are  able  to  do  by  means  of  digestive  enzymes  given  out 
by  the  rootlike  parts,  by  means  of  which  the  molds  cling  to  the 
bread.  These  digestive  enzymes  change  the  starch  of  the  bread  to 
sugar  and  the  protein  to  a  soluble  form  which  will  pass  by  osmosis 
into  cells  of  the  mold.  Thus  the  mold  is  able  to  absorb  food 
material.  These  foods  are  then  used  to  supply  energy  and  make 
protoplasm.  This  seems  to  be  the  usual  method  by  which  sapro- 
phytes make  use  of  the  materials  on  which  they  live. 


134  PLANTS  WITHOUT   CHLOROPHYLL 

What  can  Molds  live  On?  —  We  have  seen  that  black  mold 
lives  upon  bread.  We  would  find  that  it  or  some  other  mold 
(e.g.  green  or  blue  mold)  live  upon  decaying  or  overripe  fruit,  — 
apples,  peaches,  and  plums  being  especially  susceptible  to  their 
growth.  Molds  feed  upon  all  cakes  or  breads,  upon  meat,  cheese, 
and  many  raw  vegetables.  They  are  almost  sure  to  grow  upon 
flour  if  it  is  allowed  to  get  damp.  Moisture  seems  necessary  for 
their  growth.  Jelly  is  a  substance  particularly  favorable  to  molds 
for  this  reason.  Shoes,  leather,  cloth,  paper,  or  even  moist  wood 
will  give  food  enough  to  support  their  growth.  At  least  one 
troublesome  disease,  ringworm,  is  due  to  the  growth  of  molds 
in  the  skin. 

What  Mold  does  to  Foods.  —  Mold  usually  changes  the  taste 
of  the  material  it  grows  upon,  rendering  it  "  musty  "  and  some- 
times unfit  to  eat.  Eventually  it  will  spoil  food  completely  be- 
cause decay  sets  in.  Decay,  as  we  will  see  later,  is  not  entirely 
due  to  mold  growth,  but  is  usually  caused  by  another  group  of 
organisms,  the  bacteria.  Molds,  however,  in  feeding  do  cause 
chemical  changes  which  result  in  decay  or  putrefaction.  Some 
molds  are  useful.  They  give  the  flavor  to  Roquefort,  Gorgonzola, 
Camembert,  and  Brie  cheeses.  But  on  the  whole  molds  are  pests 
which  the  housekeeper  wishes  to  get  rid  of. 

How  to  prevent  Molds.^  —  As  we  have  seen,  moisture  is  favorable 
for  mold  gro^vth ;  conversely,  dryness  is  unfavorable.  Inasmuch 
as  the  spores  of  mold  abound  in  the  air,  materials  which  cannot  be 
kept  dry  should  be  covered.  Jelly  after  it  is  made  should  at  once 
be  tightly  covered  with  a  thin  layer  of  paraffin,  which  excludes  the 
air  and  possible  mold  spores.  Or  waxed  paper  may  be  fastened 
over  the  surface  of  the  jelly  so  as  to  exclude  the  spores.  To  pre- 
vent molds  from  attacking  fresh  fruit,  the  surface  of  the  fruit 
should  be  kept  dry  and,  if  possible,  each  piece  of  fruit  should  be 
wrapped  in  paper.  Why?  Heating  with  dry  heat  to  212°  for 
a  few  moments  will  kill  any  mold  spores  that  happen  to  be  in 
food.  Moldy  food,  if  heated  after  removing  surface  on  which  the 
mold  grew,  is  perfectly  good  to  eat. 

*  An  experiment  to  show  conditions  unfavorable  for  growth  of  molds  should  be 
shown  at  this  point. 


PLANTS   WITHOUT   CHLOROPHYLL  135 

Dry  dusting  or  sweeping  will  raise  dust,  which  usually  contains 
mold  spores.  Use  a  dampened  broom  or  dust  cloth  frequently  in 
the  kitchen  if  you  wish  to  preserve  foods  from  molds. 

Other  Moldlike  Fungi.  —  Mildews  are  near  relatives  of  the 
molds  found  in  our  homes.  They  may  attack  leather,  cloth,  etc., 
in  a  damp  house.  Other  allied  forms  may  do  damage  to  living 
plants.  Some  of  these  live  upon  the  lilac,  rose,  or  willow.  These 
fungi  do  not  penetrate  the  host  plant  to  any  depth,  for  they  obtain 
their  food  from  the  outer  layer  of  cells  in  the  leaf  of  their  host  and 
cover  the  leaves  with  the  whitish  threads  of  the  mycelium. 
Hence  they  may  be  killed  by  means  of  applications  of  some 
fungus-killing  fluid,  as  Bordeaux  mixture.^  Among  the  useful 
plants  preyed  upon  by  mildews  are  the  plum,  cherry,  and  peach 
trees.  (The  diseases  known  as  black  knot  and  peach  curl  are 
thus  caused.)  Another  important  member  of  this  group  is  the 
tiny  parasite  found  on  rye  and  other  grains,  which  gives  us  the 
drug  ergot. 

Among  other  parasitic  fungi  are  rusts  and  smuts.  Wheat  rust 
is  probably  the  most  destructive  parasitic  fungus.  Indirectly  this 
parasite  is  of  considerable  importance  to  the  citizen  of  a  great  city 
because  of  its  effect  upon  the  price  of  wheat. 

Yeasts  in  their  Relation  to  Man 

Fermentation.  —  It  is  of  common  knowledge  to  country  boys 
or  girls  that  the  juice  of  fresh  apples,  grapes,  and  some  other 
fruits,  if  allowed  to  stand  exposed  to  the  air  for  a  short  time  will 
ferment.  That  is,  the  sweet  juice  will  begin  to  taste  sour  and 
to  have  a  peculiar  odor,  which  we  recognize  as  that  of  alcohol. 
The  fermenting  juice  appears  to  be  full  of  bubbles  which  rise  to 
the  surface.  If  we  collect  enough  of  these  bubbles  of  gas  to  make 
a  test,  we  find  it  to  be  carbon  dioxide. 

Evidently  something  changed  some  part  of  the  apple  or  grape, 
the  sugar,  (C6H12O6),  into  alcohol,  2  (C2H6O),  and  carbon  dioxide, 
2(002).     This  chemical  process  is  known  as  fermentation. 

1  See  Goff  and  Mayne,  First  Principles  of  Agriculture,  page  50,  for  formula  of 
Bordeaux  mixture. 


136 


PLANTS  WITHOUT   CHLOROPHYLL 


Apparatus  to  show  effect  of 
fermentation.  N,  molasses, 
water  and  yeast  plants  ;  C, 
bubbles  of  carbon  dioxide. 


Yeast  causes  Fermentation.  —  Let  us  now  take  a  compressed 

yeast  cake,  shake  up  a  small  portion  of  it  in  a  solution  of  mo- 
lasses and  water,  and  fill  a  fermentation 
tube  with  the  mixture.  Leave  the  tube 
in  a  warm  place  overnight.  In  the 
morning  a  gas  will  be  found  to  have 
been  collected  in  the  closed  end  of  the 
tube  (see  Figure  on  page  138).  The 
taste  and  odor  of  the  liquid  shows 
alcohol  to  be  present,  and  the  gas,  if 
tested,  is  proven  carbon  dioxide. 
Evidently  yeast  causes  fermentation. 
What  are  Yeasts  ?  —  If  now  part  of 
the  liquid  from  the  fermentation  tube 
which  contains  the  settlings  be  drawn 
off,  a  drop  placed  on  a  slide  and  a  little 

weak  iodine  added  and  the  mixture  examined  under  the  compound 

microscope,  two  kinds  of  structures  will  be  found  (see  Figure  below), 

starch  grains  which  are  stained 

deep   blue,  and  other  smaller 

ovoid  structures  of  a  brownish 

yellow    color.     The  latter  are 

yeast  plants. 

Size  and  Shape,  Manner  of 

Growth,    etc.  —  The    common 

compressed  yeast  cake  contains 

millions  of  these   tiny  plants. 

In  its   simplest  form   a  yeast 

plant   is    a   single    cell.      The 

shape  of  such  a  plant  is  ovoid, 

each   cell   showing   under   the 

microscope    the    granular    ap- 
pearance of  the  protoplasm  of 

which  it  is  formed.     Look  for 

tiny  clear  areas  in  the   cells ; 

these  are  vacuoles,  or  spaces  filled  with  fluid.     The  nucleus  is  hard 

to  find  in  a  yeast  cell.     Many  of  the  cells  seem  to  have  others 


Yeast  and  starch  grains.  Notice  that  the 
starch  grains  around  which  are  clustered 
yeast  cells  have  been  rounded  off  by  the 
yeast  plants.  How  do  you  account 
for  this  ? 


PLANTS  WITHOUT  CHLOROPHYLL  137 

attached  to  them,  sometimes  there  being  several  in  a  row.  Yeast 
cells  reproduce  very  rapidly  by  a  process  of  budding,  a  part  of  the 
parent  cell  forming  one  or  more  smaller  daughter  cells  which  even- 
tually become  free  from  the  parent. 

Conditions  favorable  to  growth  of  Yeast.  —  Experiment.  —  Label  three 
pint  fruit  jars  A,  B,  and  C.  Add  one  fourth  of  a  compressed  yeast  cake  to 
two  cups  of  water  containing  two  tablespoonfuls  of  molasses  or  sugar. 
Stir  the  mixture  well  and  divide  it  into  three  equal  parts  and  pour  them 
into  the  jars.  Place  covers  on  the  jars.  Put  jar  A  in  the  ice  box  on  the 
ice,  and  jar  B  over  the  kitchen  stove  or  near  a  radiator ;  pour  the  contents 
of  jar  C  into  a  small  pan  and  boil  for  a  few  minutes.  Pour  back  into  C, 
cover  and  place  it  next  to  B.  After  forty-eight  hours,  look  to  see  if  any 
bubbles  have  made  their  appearance  in  any  of  the  jars.  If  the  experiment 
has  been  successful,  only  jar  B  will  show  bubbles.  After  bubbles  have 
begun  to  appear  at  the  surface,  the  fluid  in  jar  B  will  be  found  to  have  a 
sour  taste  and  will  smell  unpleasantly.  The  gas  which  rises  to  the  surface, 
if  collected  and  tested,  will  be  found  to  be  carbon  dioxide.  The  contents 
of  jar  B  have  fermented.  Evidently,  the  growth  of  yeast  will  take  place 
only  under  conditions  of  moderate  warmth  and  moisture. 

Carbohydrates  necessary  to  Fermentation.  —  Sugar  must  be 
present  in  order  for  fermentation  to  take  place.  The  wild  yeasts 
cause  fermentation  of  the  apple  or  grape  juice  because  they  live 
on  the  skin  of  the  apple  or  grape.  Various  peoples  recognize 
this  when  they  collect  the  juice  of  certain  fruits  and,  exposing 
it  to  the  air,  allow  it  to  ferment.  Such  is  the  saki  or  rice  ^vine  of 
the  Japanese,  the  tuba  or  sap  of  the  coconut  palm  of  the  Filipinos 
and  the  pulque  of  the  Mexicans. 

Beer  and  Wine  Making.  —  Brewers'  yeasts  are  cultivated  with 
the  greatest  care;  for  the  different  flavors  of  beer  seem  to  de- 
pend largely  upon  the  condition  of  the  yeast  plants.  Beer  is 
made  in  the  following  manner.  Sprouted  barley,  called  malt,  in 
which  the  starch  of  the  grain  has  been  changed  to  grape  sugar  by 
digestion,  is  killed  by  drying  in  a  hot  kiln.  The  malt  is  dissolved 
in  water,  and  hops  are  added  to  give  the  mixture  a  bitter  taste. 
Now  comes  the  addition  of  the  yeast  plants,  which  multiply  rapidly 
under  the  favorable  conditions  of  food  and  heat.  Fermentation 
results  on  a  large  scale  from  the  breaking  down  of  the  grape  sugar, 


138 


PLANTS  WITHOUT   CHLOROPHYLL 


the  alcohol  remaining  in  the  fluid,  and  the  carbon  dioxide  passing 
off  into  the  air.  At  the  right  time  the  beer  is  stored  either  in 
bottles  or  casks,  but  fermentation  slowly  continues,  forming  car- 
bon dioxide  in  the  bottles.  This  gives  the  sparkle  to  beer  when  it 
is  poured  from  the  bottle. 

In  wine  making  the  wdld  yeasts  growing  on  the  skin  of  the  grapes 
set  up  a  slow  fermentation.  It  takes  several  weeks  before  the 
wine  is  ready  to  bottle.  In  sparkling  wdnes  a  second  fermentation 
in  the  bottles  gives  rise  to  carbon  dioxide  in  such  quantity  as  to 
cause  a  decided  frothing  when  the  bottle  is  opened. 

Commercial  Yeast.  —  Cultivated  yeasts  are  now  supplied  in 
the  home  as  compressed  or  dried  yeast  cakes.  In  both  cases  the 
yeast  plants  are  mixed  with  starch  and  other  substances  and 
pressed  into  a  cake.  But  the  compressed  yeast  cake  must  be  used 
fresh,  as  the  yeast  plants  begin  to  die  rapidly  after  two  or  three 
days.  The  dried  yeast  cake,  while  it  contains  a  much  smaller 
number  of  yeast  plants,  is  nevertheless  probably  more  reliable  if 
the  yeast  cannot  be  obtained  fresh. 

The  cut  illustrates 
an  experiment  that 
shows  how  yeast 
plants  depend  upon 
food  in  order  to  grow. 
In  each  of  three  fer- 
mentation tubes  were 
placed  an  equal 
amount  of  a  com- 
pressed yeast  cake. 
Then  tube  a  was 
filled  with  distilled 
water,  tube  h  with  a 
solution  of  glucose 
and  water,  and  tube 
c  with  a  nutrient  solution  containing  nitrogenous  matter  as  well 
as  glucose.  The  quantity  of  gas  (CO2)  in  each  tube  is  an  index  of 
the  amount  of  growth  of  the  yeast  cells.  In  which  tube  did  the 
greatest  growth  take  place  ? 


PLANTS  WITHOUT  CHLOROPHYLL  139 

Bread  Making.  —  Most  of  us  are  familiar  with  the  process  of 
bread  making.  The  materials  used  are  flour,  milk  or  water  or 
both,  salt,  a  little  sugar  to  hasten  the  process  of  fermentation,  or 
*'  rising,''  as  it  is  called,  some  butter  or  lard,  and  yeast. 

After  mixing  the  materials  thoroughly  by  a  process  called  ''knead- 
ing," the  bread  is  put  aside  in  a  warm  place  (about  75°  Fahrenheit) 
to  ''  rise."  If  we  examine  the  dough  at  this  time,  we  find  it  filled 
with  holes,  which  give  the  mass  a  spongy  appearance.  The  yeast 
plants,  owing  to  favorable  conditions,  have  grown  rapidly  and  filled 
the  cavities  with  carbon  dioxide.  Alcohol  is  present,  too,  but  this 
is  evaporated  when  the  dough  is  baked.  The  baking  cooks  the 
starch  of  the  bread,  drives  off  the  carbon  dioxide  and  alcohcl,  and 
kills  the  yeast  plants,  besides  forming  a  protective  crust  on  the  loaf. 

Sour  Bread.  —  If  yeast  cakes  are  not  fresh,  sour  bread  may  result 
from  their  use.  In  such  yeast  cakes  there  are  apt  to  be  present 
other  tiny  one-celled  plants,  known  as  bacteria.  Certain  of  these 
plants  form  acids  after  fermentation  takes  place.  The  sour  taste 
of  the  bread  is  usually  due  to  this  cause.  The  remedy  would 
be  to  have  fresh  yeast,  to  have  good  and  fresh  flour,  and  to  have 
clean  vessels  with  which  to  work. 

Importance  of  Yeasts.  —  Yeasts  in  their  relation  to  man  are 
thus  seen  to  be  for  the  most  part  useful.  They  may  get  into 
canned  substances  put  up  in  sugar  and  cause  them  to  ''work," 
giving  them  a  peculiar  flavor.  But  they  can  be  easily  killed  by 
heating  to  the  temperature  of  boiling.  On  the  other  hand,  yeast 
plants  are  necessary  for  the  existence  of  all  the  great  industries 
which  depend  upon  fermentation.  And  best  of  all  they  give  us 
leavened  bread,  which  has  become  a  necessity  to  most  of  mankind. 

Bacteria  in  their  Relation  to  Man 

What  Bacteria  do  and  Where  They  May  be  Found.  —  A  walk 
through  a  crowded  city  street  on  any  warm  day  makes  one  fully 
alive  to  odors  which  pervade  the  atmosphere.  Some  of  these  un- 
pleasant odors,  if  traced,  are  found  to  come  from  garbage  pails, 
from  piles  of  decaying  fruit  or  vegetables,  or  from  some  butcher 
shop  in  which  decayed  meat  is  allowed  to  stand.  This  character- 
istic phenomena  of  decay  is  one  of  the  numerous  ways  in  which 


140 


PLANTS  WITHOUT  CHLOROPHYLL 


STERiLizirrc 


we  can  detect  the  presence  of  bacteria.  These  tiny  plants,  *'  man's 
invisible  friends  and  foes,"  are  to  be  found  "  anywhere,  but  not 
everywhere,"  in  nature.  They  swarm  in  stale  milk,  in  impure 
water,  in  soil,  in  the  living  bodies  of  plants  and  animals  and  in 
their  dead  bodies  as  well.  Most  "  catching  "  diseases  we  know 
to  be  caused  directly  by  them ;  the  processes  of  decay,  souring  of 
milk,  acid  fermentation,  the  manufacture  of  nitrogen  for  plants 

are  directly  or  indirectly  due  to 
their  presence.  It  will  be  the  pur- 
pose of  the  next  paragraphs  to 
find  some  of  the  places  where 
bacteria  may  be  found  and  how 
we  may  know  of  their  presence. 

How  we  catch  Bacteria  to  Study 
Them.  —  To  study  bacteria  it  is 
first  necessary  to  find  some  ma- 
terial in  which  they  will  grow,  then 
kill  all  living  matter  in  this  food 
material  by  heating  to  boiling 
point  (212°)  for  half  an  hour  or 
more  (this  is  called  sterilization), 
and  finally  protect  the  culture 
medium^  as  this  food  is  called,  from 
other  living  things  that  might 
grow  upon  it. 

One  material  in  which  bacteria  seem  to  thrive  is  a  mixture  of 
beef  extract,  digested  protein  and  gelatine  or  agar-agar,  the  latter 
a  preparation  derived  from  seaweed.  This  mixture,  after  ster- 
ilization, is  poured  into  flat  dishes  with  loose-fitting  covers. 
These  petri  dishes,  so  called  after  their  inventor,  are  the  traps 
in  which  we  collect  and  study  bacteria. 

Where  Bacteria  might  Grow.  —  Expose  a  number  of  these  steril- 
ized dishes,  each  for  the  same  length  of  time,  to  some  of  the  fol- 
lowing conditions : 

(a)  exposed  to  the  air  of  the  schoolroom. 

(6)  exposed  in  the  halls  of  the  school  while  pupils  are  passing. 

(c)  exposed  in  the  halls  of  the  school  when  pupils  are  not  moving. 


A  steam  sterilizer. 


PLANTS  WITHOUT  CHLOROPHYLL 


141 


(d)  exposed  at  the  level  of  a  dirty  and  much-used  city  street. 

(e)  exposed  at  the  level  of  a  well-swept  and  little-used  city  street. 
(/)  exposed  in  a  city  park. 

(g)  exposed  in  a  factory  building. 

(h)  dirt  from  hands  placed  in  dish. 

(^)  rub  interior  of  mouth  with  finger  and  touch  surface  of  dish. 

{j)  touch  surface  of  dish  with  decayed  vegetable  or  meat. 

(k)  touch  surface  of  dish  with  dirty  coin  or  bill. 

(I)  place  in  dish  two  or  three  hairs  from  boy's  head. 

This  list  might  be  prolonged  indefinitely. 

Now  let  us  place  all  of  the  dishes  together  in  a  moderately  warm 
place  (a  closet  in  the  schoolroom  will  do)  and  watch  for  results. 
After  a  day  or  two  little  spots, 
brown,  yellow,  white,  or  red,  will 
begiii  to  appear.  These  spots,  which 
grow  larger  day  by  day,  are  colonies 
made  up  of  millions  of  bacteria. 
But  probably  each  colony  arose 
from  a  single  bacterium  which  got 
into  the  dish  when  it  was  exposed 
to  the  air. 

How  we  may  isolate  Bacteria  of 
Certain  Kinds  from  Others.  —  In 
order  to  get  a  number  of  bacteria 
of  a  given  kind  to  study,  it  becomes 
necessary  to  grow  them  in  what  is 

known  as  a  pure  culture.  This  is  done  by  first  growing  the 
bacteria  in  some  medium  such  as  beef  broth,  gelatin,  or  on 
potato.^  Then  as  growth  follows  the  colonies  of  bacteria  appear 
in  the  culture  media  or  the  beef  broth  becomes  cloudy.  If  now 
we  wish  to  study  one  given  form,  it  becomes  necessary  to  isolate 
them  from  the  others.  This  is  done  by  the  following  process : 
a  platinum  needle  is  first  passed  through  a  flame  to  sterilize  it; 
that  is,  to  kill  all  living  things  that  may  be  on  the  needle  point. 

^  For  directions  for  making  a  culture  medium,  see  Hunter,  Laboratory  Problems 
in  Civic  Biology.  Culture  tubes  may  be  obtained,  already  prepared,  from  Parke, 
Davis,  and  Company  or  other  good  chemists. 


Colonies  of  bacteria  growing  in 
a  petri  dish. 


142 


PLA.NTS  WITHOUT  CHLOROPHYLL 


A  pure  culture  of  bacteria.  Notice 
that  the  bacteria  are  all  the  same 
size  and  shape. 


Then  the  needle,  which  cools  very  quickly,  is  dipped  in  a  colony 
containing  the  bacteria  we  wish  to  study.     This  mass  of  bacteria 

is  quickly  transferred  to  another 
sterilized  plate,  and  this  plate  is 
immediately  covered  to  prevent 
any  other  forms  of  bacteria  from 
^^^^^C^y^^'^'^:^^^  entering.  When  we  have  suc- 
•      ^^S»§A*^2.1?  ^."*4t,-^  ^r^^      ceeded  in  isolating  a  certain  kind  of 

bacterium  in  a  given  dish,  we  are 
said  to  have  a  pure  culture.  Hav- 
ing obtained  a  pure  culture  of 
bacteria,  they  may  easily  be  studied 
under  the  compound  microscope. 

Size  and  Form.  —  In  size,  bac- 
teria are  the  most  minute  plants 
known.  A  bacterium  of  average 
size  is  about  twoo  of  ^^  i^^^h  in 
length,  and  perhaps  s^fo  o^  ^^ 
inch  in  diameter.  Some  species 
are  much  larger,  others  smaller.  A  common  spherical  form  is 
-g^^o  of  an  inch  in  diameter.  They  are  so  small  that  several  million 
are  often  found  in  a  single  drop  of  impure  water  or  sour  milk. 
Three  well-defined  forms  of  bacteria  are  recognized :  a  spherical 
form  called  a  coccus,  sl  rod-shaped  bacterium,  the  bacillus,  and  a 
spiral  form,  the  spirillurn.  Some  bacteria  are  capable  of  move- 
ment when  living  in  a  fluid.  Such  movement  is  caused  by  tiny 
lashlike  threads  of  protoplasm  called  flagella.  The  flagella  pro- 
ject from  the  body,  and  by  a  rapid  movement  cause  locomotion 
to  take  place.  Bacteria  reproduce  with  almost  incredible  rapidity. 
It  is  estimated  that  a  single  bacterium,  by  a  process  of  division 
GSiWed  fission,  will  give  rise  to  over  16,700,000  others  in  twenty-four 
hours.  Under  unfavorable  conditions  they  stop  dividing  and  form 
rounded  bodies  called  spores.  This  spore  is  usually  protected  by 
a  wall  and  may  withstand  very  unfavorable  conditions  of  dryness  or 
heat ;  even  boiling  for  several  minutes  will  not  kill  some  forms. 

Where  Bacteria   are   most  Numerous.  —  As  the  result  of  our 
experiments,  we  can  make  some  generalizations  concerning  the 


PLANTS   WITHOUT   CHLOROPHYLL 


143 


presence  of  bacteria  in  our  own  environment.  They  are  evidently 
present  in  the  air,  and  in  greater  quantity  in  air  that  is  moving 
than  quiet  air.  Why? 
That  they  stick  to  par- 
ticles of  dust  can  be 
proven  by  placing  a 
little  dust  from  the 
schoolroom  in  a  culture 
dish.  Bacteria  are  pres- 
ent in  greater  numbers 
where  crowds  of  people 
live  and  move,  the  air 
from  dusty  streets  of  a 
populous  city  contains 
many  more  bacteria 
than  does  the  air  of  a 
village  street.  The  air 
of  a  city  park  contains 
relatively  few  bacteria 
as  compared  with  the 
near-by  street.  The  air 
of  the  woods  or  high 
mountains  fewer  still. 
Why  ?  Our  previous 
experiment  has  shown 
that  dirt  on  our  hands, 
the  mouth  and  teeth, 
decayed  meat  and  vege- 
tables, dirty  money,  the 
very  hairs  of  our  head  are 
all  carriers  of  bacteria. 

Fluids  the  Favorite  Home  of  Bacteria.  —  Tap  water,  stand- 
ing water,  milk,  vinegar,  wine,  cider  all  can  be  proven  to  con- 
tain bacteria  by  experiments  similar  to  those  quoted  above. 
Spring  or  artesian  well  water  would  have  very  few,  if  any, 
bacteria,  while  the  same  quantity  of  river  water,  if  it  held  any 
sewage,  might  contain  untold  millions  of  these  little  organisms. 


figure  to  show  the  relative  size  and  shape  of 
(1)  a  black  mold,  (2)  yeast  cells,  and  (3)  dififer- 
ent  forms  of  bacteria ;  B,  bacillus ;  C,  coccus ; 
S,  spirillum  forms.  The  yeast  and  bacteria  are 
drawn  to  scale,  they  are  much  enlarged  in  pro- 
portion to  the  black  mold,  being  actually  much 
smaller  than  the  mold  spores  seen  at  the  top  of 
the  picture. 


144 


PLANTS   WITHOUT   CHLOROPHYLL 


Foods  preferred  by  Bacteria.  —  If  bacteria  are  living  and 
contain  no  chlorophyll,  we  should  expect  them  to  obtain  protein 
food  in  order  to  grow.  Such  is  not  always  the  case,  for  some 
bacteria  seem  to  be  able  to  build  up  protein  out  of  simple  inorganic 
nitrogenous  substances.  If,  however,  we  take  several  food  sub- 
stances, some  containing  much  protein  and  others  not  so  much,  we 

will  find  that  the  bacteria  cause 
decay  in  the  proteins  almost 
at  once,  while  other  food  sub- 
stances are  not  always  attacked 
by  them. 

What  Bacteria  do  to  Foods. 
—  When  bacteria  feed  upon  a 
protein  they  use  part  of  the 
materials  in  the  food  so  that  it 
falls  to  pieces  and  eventually 
rots.  The  material  left  behind 
after  the  bacteria  have  finished 
their  meal  is  quite  different 
from  its  original  form.  It  is 
broken  down  by  the  action  of 
the  bacteria  into  gases,  fluids, 
and  some  solids.  It  has  a  characteristic  "rotten"  odor  and  it 
has  in  it  poisons  which  come  as  a  result  of  the  work  of  the  bac- 
teria. These  poisonous  wastes,  called  ptomaines,  we  shall  learn 
more  about  later. 

Conditions  Favorable  and  Unfavorable  to  the  Growth  of  Bacteria.  — ■ 
Moisture  and  Dryness.  —  Experiment  —  Take  two  beans,  remove  the  sldns, 
crush  one,  soak  the  second  bean  overnight  and  then  crush  it.  Place  in 
test  tubes,  one  dry,  the  second  with  water.  Leave  in  a  warm  place  two 
or  three  daj^s,  then  smell  each  tube.  In  which  is  decay  taking  place  ?  In 
which  tube  are  bacteria  at  work  ?     How  do  you  know  ? 

Moisture.  —  Moisture  is  an  absolute  need  for  bacterial  growth, 
consequently  keeping  material  dry  will  prevent  the  growth  of 
germs  upon  its  surface.  Foods,  in  order  to  decay,  must  contain 
enough  water  to  make  them  moist.  Bacteria  grow  most  freely 
in  fluids. 


Growth  of  bacteria  in  a  drop  of  impure 
water  allowed  to  run  down  a  sterilized 
cultvure  in  a  dish. 


PLANTS  WITHOUT  CHLOROPHYLL  145 

Light.  —  If  we  cover  one  half  of  a  petri  dish  in  which  bacteria 
are  growing  with  black  paper  and  then  place  the  dish  in  a  light 
warm  place  for  a  few  days,  the  growth  of  bacteria  in  the  light  part 
of  the  dish  will  be  found  to  be  checked,  while  growth  continues  in 
the  covered  part.  It  is  a  matter  of  common  knowledge  that  disease 
germs  thrive  where  dirt  and  darkness  exist  and  are  killed  by  any 
long  exposure  to  sunlight.  This  shows  us  the  need  of  light  in  our 
homes,  especially  in  our  bedrooms. 

Air.  —  We  have  seen  that  plants  need  oxygen  in  order  to  per- 
form the  work  that  they  do.  This  is  equally  true  of  all  animals. 
But  not  all  bacteria  need  air  to  live ;  in  fact,  some  are  killed  by 
the  presence  of  air.  Just  how  these  organisms  get  the  oxygen 
necessary  to  oxidize  their  food  is  not  well  understood.  The  fact 
that  some  bacteria  grow  without  air  makes  it  necessary  for  us  to 
use  the  one  sure  weapon  we  have  for  their  extermination,  and  that 
is  heat. 

Heat.  —  Experiment.  —  Take  four  cultures  containing  bouillon,  in- 
oculate each  tube  with  bacteria  and  plug  each  tube  with  absorbent  cotton. 
Place  one  tube  in  the  ice  box,  a  second  tube  in  a  dark  closet  at  a  moderate 
temperature,  a  third  in  a  warm  place  (about  100°  Fahrenheit),  and  boil  the 
contents  of  the  fourth  tube  for  ten  minutes,  then  place  it  with  tube  num- 
ber two.     In  which  tubes  does  growth  take  place  most  rapidly ?     Why? 

Bacteria  grow  very  slowly  if  at  all  in  the  temperature  of  an  ice 
box,  very  rapidly  at  the  room  temperature  of  from  70°  to  90° 
and  much  less  rapidly  at  a  higher  temperature.  All  bacteria 
except  those  which  have  formed  spores  can  be  instantly  killed  as 
soon  as  boiling  point  is  reached,  and  most  spores  are  killed  by  a  few 
minutes  boiling. 

Sterilization.  —  The  practical  lessons  dra^vn  from  sterilization 
are  many.  We  know  enough  now  to  boil  our  drinking  water  if 
we  are  uncertain  of  its  purity;  we  sterilize  any  foods  that  we 
believe  might  harbor  bacteria,  and  thus  keep  them  from  spoiling. 
The  industry  of  canning  is  built  upon  the  principle  of  sterilization. 

Canning.  —  Canning  is  simply  a  method  by  which  first  the 
bacteria  in  a  substance  are  killed  by  heating  and  then  the 
substance  is  put  into  vessels  into  which  no  more  bacteria  may 
gain  entrance.     This  is  usually  done  at  home  by  boiling  the  fruit 

BUNTEB,   CIV.   BI. 10 


146 


PLANTS  WITHOUT   CHLOROPHYLL 


or  vegetable  to  be  canned  either  in  salt  and  water  or  with  sugar 
and  water,  either  of  which  substances  aids  in  preventing  the  growth 
of  bacteria.  The  time  of  boiling  will  be  long  or  short,  depending 
upon  the  materials  to  be  canned.  Some  vegetables,  as  peas,  beans, 
and  corn,  are  very  difficult  to  can,  probably  because  of  spores  of 
bacteria  which  may  be  attached  to  them.  Fruits,  on  the  other 
hand,  are  usually  much  easier  to  preserve.  After  boiling  for  the 
proper  time,  the  food,  now  free  from  all  bacteria,  must  be  put  into 
jars  or  cans  that  are  themselves  absolutely  sterile  or  free  from 
germs.  This  is  done  by  first  boiling  the  jars,  then  pouring  the 
boiling  hot  material  into  the  hot  jars  and  sealing  them  so  as  to 
prevent  the  entrance  of  bacteria  later. 

Uses  of  Canning.  —  Canning  as  an  industry  is  of  immense  im- 
portance to  mankind.  Not  only  does  it  provide  him  with  fruits 
and  vegetables  at  times  when  he  could  not  otherwise  get  them, 
but  it  also  cheapens  the  cost  of  such  things.     It  prevents  the  waste 

of  nature's  products  at  a  time 
when  she  is  most  lavish  with 
them,  enabling  man  to  store 
them  and  utilize  them  later. 
Canning  has  completely 
changed  the  life  of  the  sailor 
and  the  soldier,  who  in  former 
times  used  to  suffer  from  vari- 
ous diseases  caused  by  lack  of 
a  proper  balance  of  food. 

Pasteurization.  —  Milk  is  one 
of  the  most  important  food 
supplies  of  a  great  city.  It  is 
also  one  of  the  most  difficult 
supplies  to  get  in  good  condi- 
tion. This  is  in  part  due  to 
the  fact  that  milk  is  produced 
at  long  distances  from  the  city 
and  must  be  brought  first  from 
farms  to  the  railroads,  then  shipped  by  train,  again  taken  to  the 
milk  supply  depot  by  wagon,  there  bottled,  and  again  shipped 


Pasteurizing  milk.     Why  should  this 
be  done  ? 


PLANTS   WITHOUT   CHLOROPHYLL  147 

by  delivery  wagons  to  the  consumers.  When  we  remember  that 
much  of  the  milk  used  in  New  York  City  is  forty-eight  hours 
old  and  when  we  realize  that  bacteria  grow  very  rapidly  in  milk, 
we  see  the  need  of  finding  some  way  to  protect  the  supply  so  as 
to  make  it  safe,  particularly  for  babies  and  young  children. 

This  is  done  by  pasteurization,  a  method  named  after  the 
French  bacteriologist  Louis  Pasteur.  To  pasteurize  milk  we 
heat  it  to  a  temperature  of  not  over  170°  Fahrenheit  for  from 
ten  minutes  to  half  an  hour.  By  such  a  process  all  harmful  germs 
will  be  killed  and  the  keeping  qualities  of  the  milk  greatly  length- 
ened. Most  large  milk  companies  pasteurize  their  city  supply  by 
a  rapid  pasteurization  at  a  much  higher  temperature,  but  this 
method  slightly  changes  the  flavor  of  the  milk. 

Cold  Storage.  —  Man  has  also  come  to  use  cold  to  keep  bacteria 
from  growing  in  foods.  The  ice  box  at  home  and  cold  storage  on  a 
larger  scale  enables  one  to  keep  foods  for  a  more  or  less  lengthy 
period.  If  food  is  frozen,  as  in  cold  storage,  it  might  keep  without 
growth  of  bacteria  for  years.  But  fruits  and  vegetables  cannot 
be  frozen  without  spoiling  their  flavor.  And  all  foods  after  freez- 
ing seem  particularly  susceptible  to  the  bacteria  of  decay.  For 
that  reason  products  taken  from  cold  storage  must  be  used  at  once. 

Ptomaines.  —  Many  foods  get  their  flavor  from  the  growth  of 
molds  or  bacteria  in  them.  Cheese,  butter,  the  gamey  taste  of 
certain  meats,  the  flavor  of  sauerkraut,  are  all  due  to  the  work  of 
bacteria.  But  if  bacteria  are  allowed  to  grow  so  as  to  become 
very  numerous,  the  ptomaines  which  result  from  their  growth  in 
foods  may  poison  the  person  eating  such  foods.  Frequently 
ptomaine  poisoning  occurs  in  the  summer  time  because  of  the  rapid 
growth  of  bacteria.  Much  of  the  indigestion  and  diarrhoea  which 
attack  people  during  the  summer  is  doubtless  due  to  this  kind  of 
poisoning. 

Preservatives.^  —  This  leads  us  to  ask  if  we  may  not  preserve 
food  in  ways  other  than  those  mentioned  so  as  to  protect  our- 
selves from  danger  of  ptomaine  poisoning.  Many  substances 
check  the  development  of  bacteria  and  in  this  way  they  preserve 

1  Perform  experiment  here  to  determine  the  value  of  different  preservatives. 
Use  sugar,  salt,  vinegar,  boracic  acid,  benzoic  acid,  formaldehyde,  and  alcohol. 


148  PLANTS   WITHOUT   CHLOROPHYLL 

tiie  food.  Preservatives  are  of  two  kinds,  those  harmless  to  man 
and  those  that  are  poisonous.  Of  the  former,  salt  and  sugar  are 
examples ;  of  the  latter,  formaldehyde  and  possibly  benzoic  acid. 

Sugar.  —  We  have  noted  the  use  of  sugar  in  canning.  Small 
amounts  of  sugar  will  be  readily  attacked  by  yeasts,  molds,  and 
bacteria,  but  a  40  to  50  per  cent  solution  will  effectually  keep  out 
bacteria.  Preserves  are  fruits  boiled  in  about  their  own  weight  of 
sugar.  Condensed  milk  is  preserved  by  the  sugar  added  to  it ;  so 
are  candied  and,  in  part,  dried  fruits. 

Salt.  —  Salt  has  been  used  for  centuries  to  keep  foods.  Meats 
are  smoked,  dried,  and  salted ;  some  are  put  down  in  strong  salt 
sohitions.  Fish,  especially  cod  and  herring,  are  dried  and  salted. 
The  keeping  of  butter  is  also  due  to  the  salt  mixed  with  it.  Vine- 
gar is  another  preservative.  It,  like  salt,  changes  the  flavor  of 
materials  kept  in  it  and  so  cannot  come  into  wide  use.  Spices 
are  also  used  as  preservatives. 

Harmful  Preservatives.  —  Certain  chemicals  and  drugs,  used  as 
preservatives,  seem  to  be  on  the  border  line  of  harmfulness. 
Such  are  benzoic  acid,  borax,  or  boracic  acid.  Such  drugs  may 
be  harmless  in  small  quantities,  but  unfortunately  in  canned  goods 
we  do  not  always  know  the  amount  used.  The  national  govern- 
ment in  1906  passed  what  is  known  as  the  Pure  Food  Law,  which 
makes  it  illegal  to  use  any  of  these  preservatives  (excepting  ben- 
zoic acid  in  very  small  amounts).  Food  which  contains  this 
preservative  wdll  be  so  labeled  and  should  not  be  given  to  chil- 
dren or  people  with  weak  digestion.  Unfortunately  people  do 
not  always  read  the  labels  and  thus  the  pure  food  law  is  ineffec- 
tive in  its  working.  Infrequently  formaldehyde  or  other  pre- 
servatives are  used  in  milk.  Such  treatment  renders  milk  unfit 
for  ordinary  use  and  is  an  illegal  process. 

Disinfectants.^  —  Frequently  it  becomes  necessary  to  destroy 
bacteria  which  cause  diseases  of  various  kinds.  This  process  is 
called  dismfeding .  The  substances  commonly  used  are  carbolic 
acid,  formalin  or  formaldehyde,  lysol,  and  bichloride  of  mercury, 

•  Experiment  to  determine  the  most  effective  disinfectants.  Use  tubes  of 
bouillon  containing  different  strength  solutions  of  formaldehyde,  lysol,  iodine,  car- 
bolic acid,  and  bichloride  of  mercury.    Results.     Conclusions. 


PLANTS  WITHOUT  CHLOROPHYLL 


149 


Of  these,  the  last  named  is  the  most  powerful  as  well  as  the  most 
dangerous  to  use.  As  it  attacks  metal,  it  should  not  be  used  in  a 
metal  pail  or  dish.  It  is  commonly  put  up  in  tablets  which  are 
mixed  to  form  a  1  to  1000  solution.  Such  tablets  should  be  care- 
fully safeguarded  because  of  possible  accidental  poisoning. 

Formaldehyde  used  in  liquid  form  is  an  excellent  disinfectant. 
When  burned  in  a  formalin  candle,  it  sets  free  an  intensely 
pungent  gas  which  is  often  used  for  disinfecting  sick  rooms  after 
the  patient  has  been  removed. 

Carbolic  acid  is  perhaps  the  best  disinfectant  of  all.  If  used 
in  a  solution  of  about  1  part  to  25  of  water,  it  will  not  burn  the  skin. 
It  is  of  particular  value 


to  disinfect  skin  wounds, 
as  it  heals  as  well  as 
cleanses  when  used  in  a 
weak  solution.  Its  rather 
pleasant  odor  makes  it 
useful  to  cover  up  un- 
pleasant smells  of  the 
sick  room. 

The  fumes  of  burning 
sulphur,  which  are  so 
often  used  for  disinfect- 
ing, are  of  little  real 
value. 

Bacteria  cause  Decay. 
—  Let    us    next    see    in  ^ 

what  ways  the  bacteria  O  O  I^  X  T  B  I^  H^ 

directly    influence    man  1n[  I  '^  !R  J^^!1l   E^  S 

upon    the     earth..     Have    This  shows  how  organic  matter  is  broken  down 

you  ever  stopped  to  con- 
sider what  life  would  be 
like  on  the  earth  if  things  did  not  decay  ?  The  sea  would  soon  be 
filled  and  the  land  covered  with  dead  bodies  of  plants  and  animals. 
Conditions  of  life  would  become  impossible  and  living  things  on 
the  earth  would  cease  to  exist. 

Fortunately,    bacteria,  cause    decay.     All    organic  matter,    in 


by  bacteria  so  it  may  be  used  again  by  green 
plants. 


150 


PLANTS  WITHOUT  CHLOROPHYLL 


whatever  form,  is  sooner  or  later  decomposed  by  the  action  of 
untold  millions  of  bacteria  which  live  in  the  air,  water,  and  soil. 
These  soil  bacteria  are  most  numerous  in  rich  damp  soils  contain- 
ing large  amounts  of  organic  material.  They  are  very  numerous 
around  and  in  the  dead  bodies  of  plants  and  animals.  To  a  con- 
siderable ilegree,  then,  these  bacteria  are  useful  in  feeding  upon 
these  dead  bodies,  which  otherwise  would  soon  cover  the  surface 
of  the  earth  to  the  exclusion  of  everything  else.  Bacteria  may 
thus  be  scavengers.  They  oxidize  organic  materials,  changing 
them  to  ('()m])ounds  that  can  be  absorbed  by  plants   and  used 

in  building  protoplasm.  With- 
out bacteria  and  fungi  it  would 
be  impossible  for  life  to  exist 
on  the  earth,  for  green  plants 
would  be  unable  to  get  the 
raw  food  materials  in  forms 
that  could  be  used  in  making 
food  and  living  matter.  In 
this  respect  bacteria  are  of  the 
greatest  service  to  mankind. 

Relation  to  Fermentation.--- 
They  may  incidentally,  as  a 
result  of  this  process  of  decay, 

Microscopic  appearance  of  ordinary  milk,       Continue    the    proceSS    of     fer- 

v^hTch"^.,^'  th^^"^''   ^""f    ^-^v""'^     mentation  begun  by  the  yeasts. 

v/nich  cause  the  souring  of  milk.  ^  o  j  j 

In  making  vinegar  the  yeasts 
first  make  alcohol  (see  page  135)  which  the  bacteria  change  to 
acetic  acid.  The  lactic  acid  bacteria,  which  sour  milk,  changing 
the  milk  sugar  to  an  acid,  grow  very  rapidly  in  a  warm  tempera- 
ture ;  hence  milk  which  is  cooled  immediately  and  kept  cool  or 
which  is  pasteurized  and  kept  in  a  cool  place  will  not  sour  readily. 
Why?  These  same  lactic  acid  bacteria  may  be  useful  when  they 
sour  the  milk  for  the  cheese  maker. 

Other  Useful  Bacteria.  —  Certain  bacteria  give  flavor  to  cheese 
and  butter,  while  still  other  bacteria  aid  in  the  ''  curing  "  of 
tobacco,  in  the  production  of  the  dye  indigo,  in  the  preparation  of 
certain  fibers  of  plants  for  the  market,  as  hemp,  flax,  etc.,  in  the 


PLANTS   WITHOUT   CHLOROPHYLL 


151 


rotting  of  animal  matter  from  the  skeletons  of  sponges,  and  in  the 
process  of  tanning  hides  to  make  leather. 

Nitrogen-fixing  Bacteria.  —  Still  other  bacteria,  as  we  have 
seen  before,  "  change  over  "  nitrogen  in  organic  material  in  the 
soil  and  even  the  free  nitrogen  of  the  air  so  that  it  can  be  used  by 
plants  in  the  form  of  a  compound  of  nitrogen.  The  bacteria 
living  in  tubercles  on  the 
roots  of  clover,  beans,  peas, 
etc.,  have  the  power  of 
thus  '^  fixing "  the  free 
nitrogen  in  the  air  found 
between  particles  of  soil. 
This  fact  is  made  use  of  by 
farmers  who  rotate  their 
crops,  growing  first  a  crop 
of  clover  or  other  plants 
having  root  tubercles, 
which  produce  the  bac- 
teria, then  plowing  these 
in  and  planting  another 
crop,  as  wheat  or  corn,  on 
the  same  area.  The  latter 
plants,  making  use  of  the 
nitrogen  compounds  there, 
produce  a  larger  crop  than 
when  grown  in  ground 
containing  less  nitrogenous 
material. 

Bacteria  cause  Disease.  —  The  most  harmful  bacteria  are  those 
which  cause  diseases  of  plants  and  animals.  Certain  diseases  of 
plants  —  blights,  rots,  and  wilts  —  are  of  bacterial  nature.  These 
do  much  annual  damage  to  fruits  and  other  parts  of  growing 
plants  useful  to  man  as  food.  But  by  far  the  most  important 
are  the  bacteria  which  cause  disease  in  man.  They  accomplish 
this  by  becoming  parasites  in  the  human  body.  Millions  upon 
millions  of  bacteria  exist  in  the  human  body  at  all  times  —  in  the 
mouth,  on  the  teeth,  in  the  blood,  and  especially  in  the  lower 


A  field  of  alfalfa,  a  plant  which  harbors  the 
nitrogen-fixing  bacteria. 


152 


PLANTS   WITHOUT   CHLOROPHYLL 


part  of  the  food  tube.  Some  in  the  food  tube  are  believed  to  be 
useful,  some  harmless,  and  some  harmful ;  others  in  the  mouth 
cause  decay  of  the  teeth,  while  a  few  kinds,  if  present  in  the 
body,  may  cause  disease. 

It  is  known  that  bacteria,  like  other  living  things,  feed  and  give 
off  organic  waste  from  their  own  bodies.     This  waste,  called  a  toxin, 


TuljL-rck'S  on  tlic  roots  of  the  soy  bean.     They  contain  the  nitrogen-fixing  bacteria. 
(Fletcher's  Soils.)     Copyright  by  Doubleday,  Page  and  Company. 

is  poison  to  the  host  on  which  the  bacteria  live,  and  it  is  usually 
the  production  of  this  toxin  that  causes  the  symptoms  of  disease. 
Some  forms,  however,  break  down  tissues  and  plug  up  the  small 
blood  vessels,  thus  causing  disease. 

Diseases  caused  by  Bacteria.  —  It  is  estimated  that  bacteria 
cause  annually  over  50  per  cent  of  the  deaths  of  the  human  race. 
As  we  will  later  see,  a  very  large  proportion  of  these  diseases 
might  be  prevented  if  people  were  educated  sufficiently  to 
take  the  proper  precautions  to  prevent  their  spread.  These  pre- 
cautions might  save  the  lives  of  some  3,000,000  of  people  yearly 
in  Europe  and  America.  Tuberculosis,  typhoid  fever,  diphtheria, 
pneumonia,  blood  poisoning,  diarrhea,  and  a  score  of  other  germ 
diseases  ought  not  to  exist.  A  good  deal  more  than  half  of  the 
present  misery  of  this  world  might  be  prevented  and  this  earth 
made  cleaner  and  better  by  the  cooperation  of  the  young  people 
now  growing  up  to  be  our  future  home  makers. 

How  we  take  Germ  Diseases.  —  Germ  or  contagious  diseases 
cither  enter  the  body  by  way  of  the  mouth,  nose,  or  other  body 


PLANTS   WITHOUT   CHLOROPHYLL 


153 


A  single  cell  scraped  from  the  roof  of  the  mouth 
and  highly  magnified.  The  little  dots  are 
bacteria,  most  of  which  are  harmless.  Notice 
the  comparative  size  of  bacteria  and  cell. 


openings,  or  through  a 
break  in  the  skin.  They 
maybe  carried  by  means 
of  air,  food,  or  water, 
but  are  usually  trans- 
mitted directly  from  the 
person  who  has  the 
disease  to  a  well  per- 
son. This  may  be  done 
through  personal  con- 
tact or  by  handling 
articles  used  by  the 
sick  person  or  by  drink- 
ing or  eating  foods 
which  have  received 
some  of  the  germs. 
From  this  it  follows 
that  if  we  know  the 
methods    by    which    a 

given  disease  is  communicated,  we  may  protect  ourselves  from  it 
and  aid  the  civic  authorities  in  preventing  its  spread. 

Tuberculosis.  —  The  one  disease  responsible  for  the  greatest 
number  of  deaths  —  perhaps  one  seventh   of  the  total  on  the 

globe  —  is  tuberculosis. 
It  is  estimated  that  of 
all  people  alive  in  the 
United  States  to-day, 
5,000,000  will  die  of 
this  disease.  But  this 
disease  is  slowly  but 
surely  being  overcome. 
It  is  believed  that 
within  perhaps  one 
hundred  years^  with  the 
aid  of   good    laws  and 

Deaths    from    tuberculosis    compared    with    other    cQnifQrv    livinff     it    will 
contagious   diseases   in    the   city   of   New  York  ^  ^^' 

in  1908.  be  almost  extinct. 


154 


PLANTS   WITHOUT   CHLOROPHYLL 


Tuberculosis  is  caused  by  the  growth  of  bacteria,  called  the 
tubercle  baciUi,  within  the  lungs  or  other  tissues  of  the  human  body. 
Here  they  form  little  tubers  full  of  germs,  which  close  up  the  deli- 
cate air  passages  in  the  lungs,  while  in  other  tissues  they  give  rise 
to  hip-joint  disease,  scrofula,  lupus,  and  other  diseases,  depending 
on  the  part  of  the  body  they  attack.  Tuberculosis  may  be  con- 
tracted by  taking  the  bacteria  into  the  throat  or  lungs  or  possi- 
bly by  eating  meat  or 
drinking  milk  from 
tubercular  cattle.  Es- 
pecially is  it  communi- 
cated from  a  consump- 
tive to  a  well  person  by 
kissing,  by  drinking  or 
eating  from  the  same 
cup  or  plate,  using  the 
same  towels,  or  in  com- 
ing in  direct  contact 
with  the  person  having 
the  germs  in  his  body. 
Although  there  are  al- 
ways some  of  the  germs 
in  the  air  of  an  ordinary 
city  street,  and  though 
we  may  take  some  of 
these  germs  into  our 
bodies  at  any  time,  yet 
the  bacteria  seem  able 
to  gain  a  foothold  only 
under  certain  conditions.  It  is  only  when  the  tissues  are  in  a 
worn-out  condition,  when  we  are  "  run  down,"  as  we  say,  that 
the  parasite  may  obtain  a  foothold  in  the  lungs.  Even  if  the 
disease  gets  a  foothold,  it  is  quite  possible  to  cure  it  if  it  is 
taken  in  time.  The  germ  of  tuberculosis  is  killed  by  exposure 
to  bright  sunlight  and  fresh  air.  Thus  the  course  of  the  disease 
may  be  arrested,  and  a  permanent  cure  brought  about,  by 
a  life  in  the  open  air,  the  patient  sleeping  out  of  doors,  taking 


-400 
-300- 

-  100- 

\ 

^ 

\ 

\ 

18 

50     18(oO      1870      1880     1890     1900  19 

06 

This  curve  shows  a  decreasing  death  rate  from 
tuberculosis.     Explain. 


PLANTS   WITHOUT   CHLOROPHYLL 


155 


plenty   of   nourishing   food   and   very   little   exercise.      See   also 
Chapter  XXIV. 

Typhoid  Fever.  —  One  of  the  most  common  germ  diseases  in 
this  country  and  Europe  is  typhoid  fever.  This  is  a  disease  which 
is  conveyed  by  means  of  water  and  food,  especially  milk,  oysters, 
and  uncooked  vegetables.  Typhoid  fever  germs  live  in  the  intes- 
tine and  from  there  get  into  the  blood  and  are  carried  to  all  parts 
of  the  body.  A  poison  which  they  give  off  causes  the  fever  so 
characteristic  of  the  disease.     The  germs  multiply  very  rapidly 


This  figure  shows  how  sewage  from  a  cesspool  (c)  might  get  into  the 
water  supply:  Im,  layer  of  rock;  w,  wash  water. 


in  the  intestine  and  are  passed  off  from  the  body  with  the  excreta 
from  the  food  tube.  If  these  germs  get  into  the  water  supply 
of  a  town,  an  epidemic  of  typhoid  will  result.  Among  the  recent 
epidemics  caused  by  the  use  of  water  containing  typhoid  germs 
have  been  those  in  Butler,  Pa.,  where  1364  persons  were  made  ill ; 
Ithaca,  N.  Y.,  with  1350  cases;  and  Watertown,  N.  Y.,  where 
over  5000  cases  occurred.  Another  source  of  infection  is  milk. 
Frequently  epidemics  have  occurred  which  were  confined  to  users 
of  milk  from  a  certain  dairy.  Upon  investigation  it  was  found 
that  a  case  of  typhoid  had  occurred  on  the  farm  where  the  milk 
came  from,  that  the  germs  had  washed  into  the  well,  and  that  this 
water  was  used  to  wash  the  milk  cans.  Once  in  the  milk,  the  bac- 
teria multiplied  rapidly,  so  that  the  milkman  gave  out  cultures  of 


156 


PLANTS   WITHOUT   CHLOROPHYLL 


typhoid  in  his  milk  bottles.  Proper  safeguarding  of  our  water  and 
milk  supply  is  necessary  if  we  are  to  keep  typhoid  away. 

Blood  Poisoning.  —  The  bacterium  causing  blood  poisoning 
is  another  toxin-forming  germ.  It  lives  in  dust  and  dirt  and  is 
often  found  on  the  skin.  It  enters  the  body  through  cuts  or  bruises. 
It  seems  to  thrive  best  in  less  oxygen  than  is  found  in  the  air.  It 
is  therefore  imj^ortant  not  to  close  up  mth  court-plaster  wounds 
which  such  germs  may  have  entered.  It,  with  typhoid,  is  respon- 
sible for  four  times  as  many  deaths  as  bullets  and  shells  in  time 
of  battle.  The  wonderfully  small  death  rate  of  the  Japanese  army 
in  their  war  with  Russia  was  due  to  the  fact  that  the  Japanese 
soldiers  always  boiled  their  drinking  water  before  using  it,  and 
their  surgeons  always  dressed  all  wounds  on  the  battlefield,  using 
powerful  antiseptics  in  order  to  kill  any  bacteria  that  might  have 
lodged  in  the  exposed  wounds. 

Other  Diseases.  —  Many  other  diseases  have  been  traced  to 
bacteria.     Diphtheria  is  one  of  the  best  known.     As  it  is  a  throat 

disease,  it  may  easily 


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J. 


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m    0 


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HYOE  PARK 


DORCHESTER 


0 

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MILTON 


be  conveyed  from 
one  person  to  another 
by  kissing,  putting 
into  the  mouth  ob- 
jects which  have 
come  in  contact  with 
the  mouth  of  the 
patient,  or  by  food 
into  which  the  germs 
have  been  carried. 
Grippe,    pneumonia, 


This  figure  shows  how  a  milk  route  might  be  instru- 
mental in  spreading  diphtheria.  X  is  a  farm  on 
which  a  case  of  diphtheria  occurred  that  was  re- 

fZ^JrvL^l^ZlT^^amm:.  ^Ho°w  whoopingrcough,  and 

would  you  explain  this  ?  Certain  kinds  of  colds, 

all  undoubtedly  germ 
diseases,  are  contracted  in  a  similar  manner.  Contact  with  the 
bacteria  causing  the  disease  must  occur  in  order  that  a  person 
take  the  disease.  This  may  mean  actual  contact  with  the  sick 
person  or  an  indirect  transfer  of  the  germs  by  the  means  men- 
tioned above.    The  germs  which  cause  diarrhea  of  babies,  a  disease 


PLANTS  WITHOUT   CHLOROPHYLL  157 

which  takes  such  a  toll  of  death  each  summer,  may  be  prevented 
by  pasteurizing  the  milk  before  using,  so  as  to  kill  the  harmful 
bacteria.  Other  diseases,  as  malaria,  yellow  fever,  sleeping  sick- 
ness, and  probably  smallpox,  scarlet  fever,  and  measles,  are  due 
to  the  attack  of  one-celled  animal  parasites.  Of  these  we  shall 
learn  later  in  Chapter  XV. 

Immunity.  —  It  has  been  found  that  after  an  attack  of  a  germ 
disease  the  body  will  not  soon  be  again  attacked  by  the  same 
disease.  This  immunity,  of  which  we  will  learn  more  later,  seems 
to  be  due  to  a  manufacture  in  the  blood  of  substances  which 
fight  the  bacteria  or  their  poisons.  If  a  person  keeps  his  body 
in  good  physical  condition  and  lives  carefully,  he  will  do  much 
toward  acquiring  this  natural  immunity. 

Acquired  Immunity.  —  Modern  medicine  has  discovered  means 
of  protecting  the  body  from  some  contagious  diseases.  Vaccina- 
tion as  protection  against  smallpox,  the  use  of  antitoxins  (of  which 
more  later)  against  diphtheria,  and  inoculation  against  typhoid 
are  all  ways  in  which  we  may  be  protected  against  diseases. 

Methods  of  fighting  Germ  Diseases.  —  As  we  have  seen,  dis- 
eases produced  by  bacteria  may  be  caused  by  the  bacteria  being 
directly  transferred  from  one  person  to  another,  or  the  disease 
may  obtain  a  foothold  in  the  body  from  food,  water,  or  by  taking 
them  into  the  blood  through  a  cut  or  a  wound  or  a  body  opening. 

It  is  evident  that  as  individuals  we  may  each  do  something  to 
prevent  the  spread  of  germ  diseases,  especially  in  our  homes.  We 
may  keep  our  bodies,  especially  our  hands  and  faces,  clean.  Sweep- 
ing and  dusting  may  be  done  with  damp  cloths  so  as  not  to  raise  a 
dust ;  our  milk  and  water,  when  from  a  suspicious  supply,  may  be 
sterilized  or  pasteurized.  Wounds  through  which  bacteria  might 
obtain  foothold  in  the  body  should  be  washed  with  some  antiseptic 
such  as  carbolic  acid  (1  part  to  25  water),  which  kills  the  germs. 
In  a  later  chapter  we  shall  learn  more  of  how  we  may  cooperate 
with  the  authorities  to  combat  disease  and  make  our  city  or  town 
a  better  place  in  which  to  live.^ 

1  Teachers  may  take  up  parts  or  all  of  Chapter  XXIV  at  this  point.  I  have 
found  it  advisable  to  repeat  much  of  the  work  on  bacteria  after  the  students  have 
taken  up  the  study  of  the  human  organism. 


158  PLANTS   WITHOUT   CHLOROPHYLL 


Reference  Books 


ELEMENTARY 


Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Bigelow,  Introduction  to  Biology.     The  Macmillan  Company. 

Conn,  Bacteria,  Yeasts,  and  Molds  in  the  Home.     Ginn  and  Company. 

Conn,  Story  of  Germ  Life.     D.  Appleton  and  Company. 

Davison,  The  Human  Body  and  Health.     American  Book  Company. 

Frankland,  Bacteria  in  Daily  Life.     Longmans,  Green,  and  Company. 

Overton,  General  Hygiene.     American  Book  Company. 

Pruddon,  Dust  and  its  Dangers.     G.  P.  Putnam's  Sons. 

Pruddcn,  The  Story  of  the  Bacteria.     G.  P.  Putnam's  Sons. 

Ritchie,  Primer  of  Sanitation.     World  Book  Company. 

Sharpe,  Laboratory  Manualin  Biology,  pages  123-132.    American  Book  Company. 

ADVANCED 

Conn,  Agricultural  Bacteriology.     P.  Blakiston's  Sons  and  Company. 

Coulter,  Barnes,  and  Cowles,  A  Textbook  of  Botany,  Vol.  I.     American  Book  Com- 
pany 

De  Bar>',  Comparative  Morphology  and  Biology  of  the  Fungi,  Mycetozoa,  and  Bacteria. 
Clarendon  Press. 

Duggar,  Fungous  Diseases  of  Plants.     Ginn  and  Company. 

Hough  and  Sedgwick,  The  Human  Mechanism.     Ginn  and  Company. 

Hutchinson,  Preventable  Diseases.     Houghton,  Mifflin  and  Company. 

Lee,  Scientific  Features  of  Modern  Medicine.     Columbia  University  Press. 

Muir  and  Ritchie,  Manual  of  Bacteriology.     The  Macmillan  Company. 

Newman,  The  Bacteria.     G.  P.  Putnam's  Sons. 

Sedgwick,  Principles  of  Sanitary  Science  and  Public  Health.     The  Macmillan  Com 
pany. 


XII.   THE  RELATIONS   OF  PLANTS  TO  ANIMALS 

Problems.  —  To  determine  the  general  biological  relations  ex- 
isting between  plants  and  animals. 

(a)  As  shown  in  a  balanced  aquarium. 

(b)  As  shown  in  hay  infusion. 

Suggestions  for  Laboratory  Work 

Demonstration  of  life  in  a  ^^ balanced^'  and  ^' unbalanced ^^  aquarium.  — 
Determination  of  factors  causing  balance. 

Demonstration  of  hay  infusion.  — Examination  to  show  forms  of  animal 
and  plant  life. 

Tabular  comparison  between  balanced  aquarium  and  hay  infusion. 

Some  Ways  in  which  Plants  affect  Animals.  —  We  have  been 
studying  the  life  of  plants  in  order  better  to  understand  the  life 
of  animals  and  men.  We  have  seen  first  that  green  plants  play 
indirectly  a  tremendous  part  in  man's  welfare  by  supplying  him 
with  food.  We  have  found  that  the  colorless  plants  directly 
affected  his  welfare  by  causing  disease,  and  by  causing  decay, 
thus  making  usable  the  nitrogen  locked  up  in  dead  bodies  of  plants 
and  animals,  and  by  some  even  supplying  nitrogen  from  the  at- . 
mosphere.  The  dependence  of  animals  upon  plants  has  been 
shown  and  the  interdependence  of  plants  on  animals  has  also  been 
seen  in  cross-pollination  and  in  the  supply  of  raw  food  materials 
to  plants  by  animals. 

Study  of  a  Balanced  Aquarium.  -7-  Perhaps  the  best  way  for  us 
to  understand  the  interrelation  between  plants  and  animals  is  to 
study  an  aquarium  in  which  plants  and  animals  live  and  in  which 
a  balance  has  been  established  between  the  plant  life  on  one  side 
and  animal  life  on  the  other.  Aquaria  containing  green  pond 
weeds,  either  floating  or  rooted,  a  few  snails,  some  tiny  animals 
known  as  water  fleas,  and  a  fish  or  two  will,  if  kept  near  a  light 
window,  show  this  relation. 

159 


160     THE   RELATIONS   OF  PLANTS  TO   ANIMALS 

We  have  seen  that  green  plants  under  favorable  conditions  of 
sunlight,  heat,  moisture,  and  with  a  supply  of  raw  food  materials, 
give  off  oxygen  as  a  bj-product  while  manufacturing  food  in  their 
green  cells.  We  know  the  necessary  raw  materials  for  starch 
manufacture  are  carbon  dioxide  and  water,  while  nitrogenous 
material  is  necessary  for  the  making  of  proteins  within  the  plant. 


A  balanced  aquarium.     Explain  the  term  "  balanced." 


In  previous  experiments  we  have  proved  that  carbon  dioxide  is 
given  off  by  any  living  thing  when  oxidation  occurs  in  the  body. 
The  crawling  snails  and  the  swiirtfiing  fish  give  off  carbon  dioxide, 
which  is  dissolved  in  the  water ;  the  plants  themselves,  at  all  times, 
oxidize  food  within  their  bodies,  and  so  must  pass  off  some  car- 
bon dioxide.  The  green  plants  in  the  daytime  use  up  the  carbon 
dioxide  obtained  from  the  various  sources  and,  with  the  water 


THE   RELATIONS  OF   PLANTS  TO   ANIMALS     161 


Ll^ 


taken  in,  manufacture  starch.  While  this  process  is  going  on,  oxy- 
gen is  given  off  to  the  water  of  the  aquarium,  and  this  free  oxygen 
is  used  by  the  animals  there. 

But  the  plants  are  continually  growing  larger.  The  snails  and 
fish,  too,  eat  parts  of  the  plants.  Thus  the  plant  life  gives  food 
to  the  animals  within  the  aquarium. 
The  animals  give  off  certain  ni- 
trogenous wastes  of  which  we  shall 
learn  more  later.  These  materials, 
with  other  nitrogenous  matter  from 
the  dead  parts  of  the  plants  or 
animals,  form  part  of  the  raw 
material  used  for  protein  manu- 
facture in  the  plant.  This  nitrog- 
enous matter  is  prepared  for  use 
by  several  different  kinds  of  bac- 
teria which  first  break  the  dead 
bodies  down  and  then  give  it  to 
the  plants  in  the  form  of  soluble 
nitrates.  The  green  plants  manu- 
facture food,  the  animals  eat  the  plants  and  give  off  organic  waste, 
from  which  the  plants  in  turn  make  their  food  and  living  matter. 

The  plants  give  off  oxygen  to  the 
animals,  and  the  animals  give  car- 
bon dioxide  to  the  plants.  Thus  a 
balance  exists  between  the  plants 
and  animals  in  the  aquarium.  Make 
a  table  to  show  this  balance. 

Relations  between  Green  Plants 
and  Animals.  —  What  goes  on  in 
the  aquarium  is  an  example  of  the 
relation  existing  between  all  green 
plants  and  all  animals.  Every- 
where in  the  world  green  plants 
are  making  food  which  becomes,  sooner  or  later,  the  food  of 
animals.  Man  does  not  feed  to  a  great  extent  upon  leaves,  but 
he  eats  roots,  stems,  fruits,  and  seeds.     When  he  does  not  feed 

HUNTER,  CIV.  BI.  —  11 


This  diagram  shows  that  plants  and 
animals  on  the  earth  hold  the 
same  relation  to  each  other  as 
plants  and  animals  in  a  balanced 
aquarium.  Explain  the  diagram 
in  your  notebook. 


Energy 
(itav) 


The  carbon  and  oxygen  cycle  in  the 
balanced  aquarium.  Trace  by 
means  of  the  arrows  the  carbon 
from  the  time  plants  take  it  in 
as  CO2  until  animals  give  it  off. 
Show  what  happens  to  the  ox;ygen. 


162     THE   RELATIONS   OF   PLANTS   TO   ANIMALS 


directly  ii])oii  plants,  lie  eats  the  flesh  of  i)lant  eating  animals, 
which  in  turn  feed  directly  upon  i)lants.  And  so  it  is  the  world 
over;    the  j^lants  are  the  food  makers  and  supply  the  animals. 


Carbon  dioxide 
(COo) 


Carbon  dioxide 
A  (COo) 


Water 

v(H«0) 


Water 
(H2O) 


Ammonia 

(nhJ 


Ammonia 


/  t  \ 

Energy  from  sun* 


ids  etc 


imal 


/     I    \ 

Energy  set  free 
as  heat. 

The  relations  between  green  plants  and  animals. 

Green  plants  also  give  a  very  considerable  amount  of  oxygen  lo 
the  atmosphere  every  day,  which  the  animals  may  use. 

The  Nitrogen  Cycle.  —  The  animals  in  their  turn  supply  much 
of  the  carbon  dioxide  that  the  plant  uses  in  starch  making.     They 

also  supply  some  of  the 
nitrogenous  matter  used  by 
the  plants,  part  being  given 
the  plants  from  the  dead 
bodies  of  their  own  rela- 
tives and  part  being  pre- 
pared from  the  nitrogen  of 
the  air  through  the  agency 
of  bacteria,  which  live 
upon  the  roots  of  certain 
plants.  These  bacteria  are 
the  only  organisms  that 
can  take  nitrogen  from 
the  air.  Thus,  in  spite  of  all  the  nitrogen  of  the  atmosphere, 
plants  and  animals  are  limited  in  the  amount  available.     And  the 


Nitric  Bacteria 


The  nitrogen  cycle.  Trace  the  nitrogen  from 
its  source  in  the  air  until  it  gets  back  again 
into  the  air. 


THE  RELATIONS  OF   PLANTS  TO    ANIMALS     163 

available  supply  is  used  over  and  over  again,  perhaps  in  nitrog- 
enous food  by  an  animal,  then  it  may  be  given  off  as  organic 
waste,  get  into  the  soil,  and  be  taken  up  by  a  plant  through  the 
roots.  Eventually  the  nitrogen  forms  part  of  the  food  supply  in 
the  body  of  the  plant,  and  then  may  become  part  of  its  living 
matter.  When  the  plant  dies,  the  nitrogen  is  returned  to  the  soil. 
Thus  the  usable  nitrogen  is  kept  in  circulation.^ 

Symbiosis.  —  We  have  seen  that  in  the  balanced  aquarium 
the  animals  and  plants,  in  a  wide  sense,  form  a  sort  of  unconscious 
partnership.  This  process  of  living  together  for  mutual  advantage 
is  called  symbiosis.  Some  animals  thus  combine  with  plants ; 
for  example,  the  tiny  animal  known  as  the  hydra  with  certain  of 
the  one-celled  algae,  and,  if  we  accept  the  term  in  a  wide  sense,  all 
green  plants  and  animals  live  in  this  relation  of  mutual  give  and 
take.  Animals  also  frequently  live  in  this  relation  to  each  other, 
as  the  crab,  which  lives  within  the  shell  of  the  oyster;  the  sea 
anemones,  which  are  carried  around  on  the  backs  of  some  hermit 
crabs,  aiding  the  crab  in  protecting  it  from  its  enemies,  and  being 
carried  about  by  the  crab  to  places  where  food  is  plentiful. 

A  Hay  Infusion.  —  Still  another  example  of  the  close  relation 
between  plants  and  animals  may  be  seen  in  the  study  of  a  hay 
infusion.  If  we  place  a  wisp  of  hay  or  straw  in  a  small  glass  jar 
nearly  full  of  water,  and  leave  it  for  a  few  days  in  a  warm  room, 
certain  changes  are  seen  to  take  place  in  the  contents  of  the  jar; 
after  a  little  while  the  water  gets  cloudy  and  darker  in  color,  and  a 
scum  appears  on  the  surface.  If  some  of  this  scum  is  examined 
under  the  compound  microscope,  it  will  be  found  to  consist  almost 
entirely  of  bacteria.  These  bacteria  evidently  aid  in  the  decay 
which  (as  the  unpleasant  odor  from  the  jar  testifies)  is  beginning 
to  take  place.  As  we  have  learned,  bacteria  flourish  wherever  the 
food  supply  is  abundant.  The  water  within  the  jar  has  come  to 
contain  much  of  the  food  material  which  was  once  within  the 
leaves  of  the  grass,  —  organic  nutrients,  starch,  sugar,  and  pro- 
teins, formed  in  the  leaf  by  the  action  of  the  sun  on  the  chlorophyll 

1 A  small  amount  of  nitrogen  gas  is  returned  to  the  atmosphere  by  the  action  of 
the  decomposing  bacteria  on  the  ammonia  compounds  in  the  soil.  (See  figure  of 
nitrogen  cycle.) 


164     THE  RELATIONS  OF  PLANTS  TO  ANIMALS 

of  the  leaf,  and  now  released  into  the  water  by  the  breaking  down 
of  the  walls  of  the  cells  of  the  leaves.  The  bacteria  themselves 
release  this  food  from  the  hay  by  causing  it  to  decay.  After  a 
few  days  small  one-celled  animals  appear;  these  multiply  with 
wonderful  rapidity,  so  that  in  some  cases  the  surface  of  the  water 
seems  to  be  almost  white  with  active  one-celled  forms  of  life.  If 
we  ask  ourselves  where  these  animals  come  from,  we  are  forced 


life  in  the  late  stage  of  a  hay  infusion.  B,  bacteria,  swimming  or  forming  masses 
of  food  upon  which  the  one-celled  animals,  the  paramcecia,  are  feeding; 
G,  gullet;  F.V.,  food  vacuole;  C.V.,  contractile  vacuole;  P,  pleurococcu"* 
P.D.,  pleurococcus  dividing.     (Drawn  from  nature  by  J.  W.  Teitz.) 


to  the  conclusion  that  they  must  have  been  in  the  water,  in  the 
air,  or  on  the  hay.  Hay  is  dried  grass  and  may  have  been  cut 
in  a  field  near  a  pool  containing  these  creatures.  When  the 
pool  dried  up,  the  wind  may  have  scattered  some  of  these  little 
organisms  in  the  dried  mud  or  dust.  Some  may  have  existed  in 
a  dormant  state  on  the  hay  and  the.water  awakened  them  to  active 


THE   RELATIONS   OF   PLANTS  TO   ANIMALS     165 

life.     In  the  water,  too,  there  may  have  been  some  living  cells, 
plants  and  animals. 

At  first  the  multiplication  of  the  tiny  animals  within  the  hay 
infusion  is  extremely  rapid ;  there  is  food  in  abundance  and  near 
at  hand.  After  a  few  days  more,  however,  several  kinds  of  one- 
celled  animals  may  appear,  some  of  which  prey  upon  others.  Con- 
sequently a  struggle  for  life  takes  place,  which  becomes  more  and 
more  intense  as  the  food  from  the  hay  is  used  up.  Eventually 
the  end  comes  for  all  the  animals  unless  some  green  plants  obtain 
a  foothold  within  the  jar.  If  such  a  thing  happens,  food  will  be 
manufactured  within  their  bodies,  a  new  food  supply  arises  for  the 
animals  within  the  jar,  and  a  balance  of  life  may  result. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Sharpe,  A  Laboratory  Manual  for  the  Solution  of  Problems  in  Biology,  pp.  133-138. 
American  Book  Company. 

ADVANCED 

Eggeriin  and  Ehrenberg,  The  Fresh  Water  Aquarium  and  its  Inhabitants.     Henry 

Holt  and  Company. 
Furneaux,  Life  in  Ponds  and  Streams.     Longmans,  Green,  and  Company. 
Parker,  Biology.     The  Macmillan  Company. 
Sedgwick  and  Wilson,  Biology.     Henry  Holt  and  Company. 


XIII.   SINGLE-CELLED     ANIMALS     CONSIDERED     AS 

ORGANISMS 

Problems,  — To  deterinifie: 

(a)  How  a  one-celled  animal  is  influenced  by  its  environ- 
ment. 

(b)  How  a  single  cell  performs  its  functions. 

(c)  TJie  structure  of  a  single-celled  animal. 

Laboratory  Suggestions 

Laboratory  study.  —  Study  of  paramoecium  under  compound  microscope 
in  its  relation  to  food,  oxygen,  etc.  Determination  of  method  of  move- 
ment, turning,  avoiding  obstructions,  sensitiveness  to  stimuli.  Drawings 
to  illustrate  above  points. 

Laboratory  demonstration.  —  Living  paramoeicium  to  show  structure  of 
cell.  Demonstration  with  carmine  to  show  food  vacuoles,  and  action  of 
cilia.  Use  of  charts  and  stained  specimens  to  show  other  points  of  cell 
structure.     Laboratory  demonstration  of  fission. 

The  Simplest  Plants.  —  We  have  seen  that  perhaps  the  simplest 
plant  would  be  exemplified  by  one  of  the  tiny  bacteria  we  have 
just  read  about.  A  typical  one-celled  plant,  however,  would 
contain  green  coloring  matter  or  chlorophyll,  and  would  have  the 
power  to  manufacture  its  own  food  under  conditions 
giving  it  a  moderate  temperature,  a  supply  of  water, 
oxygen,  carbon  dioxide,  and  sunHght.  Such  a  sim- 
ple plant  is  the  pleurococcus,  the  tiny  green  plants 
Pieurococcus.  A  seen  on  the  shady  sides  of  trees,  stones,  or  city 
pb!nt  ceiL  ^  ^  houses.  Thls  plant  would  meet  one  definition  of  a 
cell,  as  it  is  a  minute  mass  of  protoplasm  contain- 
ing a  nucleus.  It  is  surrounded  by  a  wall  of  a  woody  material 
formed  by  the  activity  of  the  living  matter  within  the  cell.  It  also 
contains  a  little  mass  of  protoplasm  colored  green.  Of  the  work 
of  the  chlorophyll  in  the  manufacture  of  organic  food  we  have 

166 


SINGLE-CELLED  ANIMALS  AS  ORGANISMS     167 

already  learned.  Such  is  a  simple  plant  cell.  Let  us  now 
examine  a  simple  animal  cell  in  order  to  compare  it  with  that 
of  a  plant. 

Where  to  find  Paramoecium.  —  If  we  examine  very  carefully 
the  surface  of  a  hay  infusion,  we  are  likely  to  notice  in  addition  to 
the  scum  formed  of  bacteria,  a  mass  of  whitish  tiny  dots  collected 
along  the  edge  of  the  jar  close  to  the  surface  of  the  water.  More 
attentive  observation  shows  us  that  these  objects  move,  and  that 
they  are  never  found  far  from  the  surface. 

The  Life  Habits  of  Paramoecium.  —  If  we  place  on  a  slide  a  drop 
of  water  containing  some  of  these  moving  objects  and  examine 
it  under  the  compound  microscope,  we  find  each  minute  whitish 
dot  is  a  cell,  elongated,  oval,  or  elliptical  in  outline  and  somewhat 
flattened.  This  is  a  one-celled  animal  known  as  the  'paramoecium 
or  the  slipper  animalcule  (because  of  its  shape) . 

Seen  under  the  low  power  of  the  microscope,  it  appears  to  be 
extremely  active,  rushing  about  now  rapidly,  now  more  slowly, 
but  seemingly  always  taking  a  definite  course.  The  narrower  end 
of  the  body  (the  anterior)  usually  goes  first.  If  it  pushes  its  way 
past  any  dense  substance  in  the  water,  the  cell  body  is  seen  to 
change  its  shape  temporarily  as  it  squeezes  through. 

Response  to  Stimuli.  —  Many  of  these  little  creatures  may  be 
found  collected  around  masses  of  food,  showing  that  they  are  at- 
tracted by  it.  In  another  part  of  the  slide  we  may  find  a  number 
of  the  paramoecia  lying  close  to  the  edge  of  an  air  bubble  with 
the  greatest  possible  amount  of  their  surface  exposed  to  its 
surface.  These  animals  are  evidently  taking  in  oxygen  by 
osmosis.  They  are  breathing.  A  careful  inspection  of  the  jar 
containing  paramoecia  shows  thousands  of  tiny  whitish  bodies 
collected  near  the  surface  of  the  jar.  In  the  paramoecium,  as 
in  the  one-celled  plants,  the  protoplasm  composing  the  cell 
responds  to  certain  agencies  acting  upon  it,  coming  from  ^vithout ; 
these  agencies  we  call  stimuli.  Such  stimuli  may  be  light,  differ- 
ences of  temperature,  presence  of  food,  electricity,  or  other  factors 
of  its  surroundings.  Plant  and  animal  cells  may  react  differently 
to  the  same  stimulus.  In  general,  however,  we  know  that  proto- 
plasm is  irritable  to  some  of  these  factors.     To  severe  stimuli, 


168     SINGLE-CELLED  ANIMALS  AS   ORGANISMS 


c.V: 


co.v 


Tp.a.n 


m. 


yrturvrt  !t7?7^-T'.>, 


protoplasm  usually  responds  by  contracting,  another  power  which 
it  possesses.  We  know,  too,  that  plant  and  animal  cells  take  in 
food  and  change  the  food  to  protoplasm,  that  is,  that  they  assimi- 
late food ;  and  that  they  may  waste  away  and  repair  themselves. 
Finally,  we  know  that  new  plant  and  animal  cells  are  reproduced 
from  the  original  bit  of  protoplasm,  a  single  cell. 

The    Structure    of   Paramoecium.  —  The    cell    body   is   almost 
transparent,   and  consists  of  semifluid  protoplasm  which  has  a 

granular  grayish  appearance  under  the 
microscope.  This  protoplasm  appears  to 
be  bounded  by  a  very  delicate  membrane 
through  which  project  numerous  delicate 
threads  of  protoplasm  called  cilia.  (These 
are  usually  invisible  under  the  micro- 
scope). 

The  locomotion  of  the  paramoecium  is 
caused  by  the  movement  of  these  cilia, 
which  lash  the  water  like  a  multitude  of 
tiny  oars.  The  cilia  also  send  particles 
of  food  into  a  funnel-like  opening,  the 
gullet,  on  one  side  of  the  cell.  Once  in- 
i^  paramoecium.  c.r,,contrac-    side  the  cell  body,  the  particles  of  food 

tile     vacuole;      f.v.,    food  j.      •    i  j.t_         j     •    j.       txxi       t-    n 

vacuole;  m,  mouth;  ma.n.,    materials    are  gathered  mto  little   balls 
macronucieus;  mi.n.,  mi-    within    the    almost    transparent    proto- 

cronucleus;       w.v.,    water        i  rm  i*  i*       i  j.     i 

vacuole.  plasm.     1  hese  masses  of  food  seem  to  be 

inclosed  within  a  little  area  containing 
fluid,  called  a  vacuole.  Other  vacuoles  appear  to  be  clear ;  these 
are  spaces  in  which  food  has  been  digested.  One  or  two  larger 
vacuoles  may  be  found;  these  are  the  contractile  vacuoles;  their 
purpose  seems  to  be  to  pass  off  waste  material  from  the  cell 
body.  This  is  done  by  pulsation  of  the  vacuole,  which  ultimately 
bursts,  passing  fluid  waste  to  the  outside.  Solid  wastes  are  passed 
out  of  the  cell  in  somewhat  the  same  manner.  No  breathing 
organs  are  seen,  because  osmosis  of  oxygen  and  carbon  dioxide 
may  take  place  anywhere  through  the  cell  membrane.  The 
nucleus  of  the  cell  is  not  easily  visible  in  living  specimens. 
In  a  cell  that  has  been  stained  it  has  been  found  to  be  a  double 


SINGLE-CELLED  ANIMALS  AS  ORGANISMS     169 


MAC. 
MIC. 


fission.  M,  mouth  ; 
MAC,  macronucleus ; 
MIC,  micronucleus. 
(After  Sedgwick  and 
Wilson.) 


structure,  consisting  of  one  large  and  one 
small  portion,  called,  respectively,  the  ma- 
cronucleus and  the  micronucleus. 

Reproduction  of  Paramoecium.  —  Some- 
times a  paramoecium  may  be  found  in  the 
act  of  dividing  by  the  process  known  as 
fission,  to  form  two  new  cells,  each  of  which 
contains  half  of  the  original  cell.  This  is  a 
method  of  asexual  reproduction.  The  origi- 
nal cell  may  thus  form  in  succession  many 
hundreds  of  cells  in  every  respect  like  the  Paramoecium  dividing  by 
original  parent  cell. 

Amoeba.^  —  In  order  to  understand  more 
fully  the  life  of  a  simple  bit  of  protoplasm, 
let  us  take  up  the  study  of  the  amceha,  a 
tjqje  of  the  simplest  form  of  animal  life.     Unlike  the  plant  and 
animal  cells  we  have  examined,  the  amoeba  has  no  fixed  form. 

Viewed  under  the  compound  micro- 
scope, it  has  the  appearance  of  an 
irregular  mass  of  granular  proto- 
plasm. Its  form  is  constantly 
changing  as  it  moves  about.  This 
is  due  to  the  pushing  out  of  tiny 
projections  of  the  protoplasm  of 
the  cell,  called  pseudopodia  (false 
feet).  The  locomotion  is  accom- 
plished by  a  streaming  or  flowing 
of  the  semifluid  protoplasm.  The 
pseudopodia  are  pushed  forward  in 
,.    ,„,  the  direction  which  the  animal  is 

Amoeba,  with  pseudopodia   {F.)   ex- 
tended ;  EC,  ectoplasm  ;  END,  en-  to  gO,  the  rest  ot   the    body   tollow- 
doplasm;    the   dark    area    (A^.)    is  l^„       J^    the    Central    part    of    the 
the  nucleus.     (From  a  photograph  ii      .  i  mi  • 
loaned  by  Professor  G.N.  Calkins.)  Cell     IS     the      nUCleUS.         I  hlS      im- 


1  Amoebae  may  be  obtained  from  the  hay  infusion,  from  the  dead  leaves  in  the  bot- 
tom of  small  pools,  from  the  same  source  in  fresh-water  aquaria,  from  the  roots  of 
duckweed  or  other  small  water  plants,  or  from  green  algae  growing  in  quiet  localities. 
No  sure  method  of  obtaining  them  can  be  given. 


170     SINGLE-CELLED   ANIMALS   AS   ORGANISMS 


portant  organ  is  difficult  to  see,  except  in  cells  that  have  been 

stained. 

Although  but  a  single  cell,  still  the  amoeba  appears  to  be  aware 
of  the  existence  of  food  when  it  is  near  at  hand.  Food  may  be 
taken  into  the  body  at  any  point,  the  semifluid  protoplasm  simply 
rolling  over  and  engulfing  the  food  material.  Within  the  body, 
as  in  the  paramoecium,  the  food  becomes  inclosed  within  a  fluid 
space  or  vacuole.  The  protoplasm  has  the  power  to  take  out  such 
material  as  it  can  use  to  form  new  protoplasm  or  give  energy. 

Circulation  of  food  material  is 
accomplished  by  the  constant 
streaming  of  the  protoplasm 
within  the  cell. 

The    cell    absorbs    oxygen 
from   the   water   by   osmosis 
through     its     delicate    mem- 
brane, giving  up  carbon  dioxide 
return.       Thus     the     cell 


m 

"  breathes  "  through  any  part 

of  its  body  covering. 

Waste  nitrogenous  products 
formed  within  the  cell  when 
work  is  done  are  passed  out 
by  means  of  the  contractile 
vacuole. 

The  amoeba,  like  other  one- 
celled  organisms,  reproduces 
by  the  process  of  fission.  A 
single  cell  divides  by  splitting 
into  two  others,  each  of  which 
resembles  the  parent  cell,  except  that  they  are  of  less  bulk. 
When  these  become  the  size  of  the  parent  amoeba,  they  each  in 
turn  divide.     This  is  a  kind  of  asexual  reproduction. 

When  conditions  unfavorable  for  life  come,  the  amoeba,  like 
some  one-celled  plants,  encysts  itself  within  a  membranous 
wall.  In  this  condition  it  may  become  dried  and  be  blown 
through  the  air.     Upon  return  to  a  favorable  environment,  it 


Amoeba,  showing  the  changes  which  take 
place  during  division  of  the  cell.  The 
dark  body  in  each  figure  is  the  nu- 
cleus ;  the  transparent  circle,  the  con- 
tractile vacuole ;  the  large  granular 
masses,  the  food  vacuoles.  Much 
magnified. 


SINGLE-CELLED    ANIMALS   AS    ORGANISMS     171 


begins  life  again,  as  before.     In  this  respect  it    resembles  the 
spore  of  a  plant. 

The  Cell  as  a  Unit.  —  In  the  daily  life  of  a  one-celled  animal  we 
find  the  single  cell  performing  all  the  general  activities  which  we 
shall  later  find  the  many-celled  animal  is  able  to  perform.  In  the 
amoeba  no  definite  parts  of  the 
cell  appear  to  be  set  off  to  per- 
form certain  functions ;  but 
any  part  of  the  cell  can  take  in 
food,  can  absorb  oxygen,  can 
change  the  food  into  proto- 
plasm, and  excrete  the  waste 
material.  The  single  cell  is,  in 
fact,  an  organism  able  to  carry 
on  the  business  of  living  almost 
as  effectually  as  a  very  com- 
plex animal. 

Complex  One-celled  Ani- 
mals. —  In  the  paramoecium 
we  find  a  single  cell,  but  we 
find  certain  parts  of  the  cell 
having  certain  definite  func- 
tions :  the  cilia  are  used  for 
locomotion ;  a  definite  part  of 
the  cell  takes  in  food,  while  the 
waste  passes  out  at  another 
definite  spot.  In  another  one- 
celled  animal  called  vorticella, 
part  of  the  cell  has  become 
elongated  and  is  contractile. 
By  this  stalk  the  little  animal 
is  fastened  to  a  water  plant  or  other  object.  The  stalk  may  be  said 
to  act  like  a  muscle  fiber,  as  its  sole  function  seems  to  be  move- 
ment; the  cilia  are  located  at  one  end  of  the  cell  and  serve  to 
create  a  current  of  water  which  will  bring  food  particles  to  the 
mouth.  Here  we  have  several  parts  of  the  cell,  each  doing  a  dif- 
ferent kind  of  work.     Thi«  is  known  as  physiological  division  of  labor. 


Vorticella.  e,  gullet;  n,  nucleus;  cv,  con- 
tractile vacuole ;  a,  axis  ;  s,  sheath ;  fv, 
food  vacuole.  (From  Herrick's  General 
Zoology.) 


172     SINGLE-CELLED   ANIMALS  AS  ORGANISMS 

Habitat  of  Protozoa.  —  Protozoa  are  found  almost  everywhere 
in  shallow  water,  especially  close  to  the  surface.  They  appear 
to  be  attracted  near  to  the  surface  by  the  supply  of  oxygen. 
Every  fresh-water  lake  swarms  with  them;  the  ocean  contains 
countless  mjTiads  of  many  different  forms. 

Use  as  Food.  —  They  are  so  numerous  in  lakes,  rivers,  and  the 
ocean  as  to  form  the  food  for  many  animals  higher  in  the  scale  of 
life.  Almost  all  fish  that  do  not  take  the  hook  and  that  travel 
in  schools,  or  companies,  migrating  from  one  place  to  another, 
live  partly  on  such  food.  Many  feed  on  slightly  larger  animals, 
which  in  turn  eat  the  Protozoa.  Such  fish  have  on  each  side  of  the 
mouth  attached  to  the  gills  a  series  of  small  structures  looking  like 
tiny  rakes.  These  are  called  the  gill  rakers,  and  aid  in  collecting 
tiny  organisms  from  the  water  as  it  passes  over  the  gills.  The 
whale,  the  largest  of  all  mammals,  strains  protozoans  and  other 
small  animals  and  plants  out  of  the  water  by  means  of  hanging 
plates  of  whalebone  or  baleen,  the  slender  filaments  of  which  form 
a  sieve  from  the  top  to  the  bottom  of  the  mouth. 

Protozoa  cause  Disease.  —  Protozoa  of  certain  kinds  play  an 
important  part  in  causing  malaria,  yellow  fever,  and  other  diseases, 
as  we  shall  see  later.^     (See  page  217.) 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.    American  Book  Company. 
Davison,  Human  Body  and  Health.     American  Book  Company. 
Jordan,  Kellogg  and  Heath,  Animal  Studies.    D.  Appleton  and  Company. 
Sharpe,  Laboratory  Manual,  pp.  140-143.     American  Book  Company. 

ADVANCED 

Calkins,  The  Protozoa.     Macmillan  Company. 

Jennings,  Study  of  the  Lower  Organisms.     Carnegie  Institution  Report. 

Parker,  LessoTis  in  Elementary  Biology.     The  Macmillan  Company. 

Wilson,  The  Cell  in  Development  and  Inheritance.    The  Macmillan  Company. 

1  Teachers  may  find  it  expedient  to  take  up  the  study  of  protozoan  diseases  at 
this  point. 


XIV.   DIVISION  OF  LABOR.     THE  VARIOUS  FORMS  OF 

PLANTS  AND   ANIMALS 

Problems.  —  The  development  and  forms  of  plants. 
The  development  of  a  simple  animal. 
What  is  division  of  labor  ?    In  what  does  it  result  ? 
How  to  know  the  ehief  chara^eters  of  some  great  animal 
groups. 

Laboratory  Suggestions 

A  visit  to  a  botanical  garden  or  laboratory  demonstration.  —  Some  of  the 
forms  of  plant  life.  Review  of  essential  facts  in  development  of  bean 
or  corn  embryo. 

Demonstration.  —  Charts  or  models  showing  the  development  of  a  many- 
celled  animal  from  egg  through  gastrula  stage. 

Demonstration.  —  Types  which  illustrate  increasing  complexity  of  body 
form  and  division  of  labor. 

Museum  trip.  —  To  afford  pupil  a  means  of  identification  of  examples 
of  principal  phyla.  This  should  be  preceded  by  objective  demonstration 
work  in  school  laboratory. 

Reproduction  in  Plants.  —  Although  there  are  very  many 
plants  and  animals  so  small  and  so  simple  as  to  be  composed  of 
but  a  single  cell,  by  far  the  greater  part  of  the  animal  and  plant 
world  is  made  up  of  individuals  which 
are  collections  of  cells  living  together. 

In  a  simple  plant  like  the  pond  scum, 

,    •  ni  i.      r        11      •      ^  J     A    cell    of    pond    scum.      How 

a  strmg  or  filament  of  cells  is  formed       ^.^^^  -^  ^^^^^  ^^  ^^^^  ^  i^^g 
by  a  single  cell  dividing  crosswise,  the       thread  made  up  of  cells  ? 
two  cells  formed  each  dividing  into  two 

more.  Eventually  a  long  thread  of  cells  is  thus  formed.  At  times, 
however,  a  cell  is  formed  by  the  union  of  two  cells,  one  from  each 
of  two  adjoining  filaments  of  the  plant.  At  length  a  hard  coat 
forms  around  this  cell,  which  has  now  become  a  spore.  The 
fcough  covering  protects  it  from  unfavorable  changes  in  the  sur- 

173 


174 


DIVISION   OF   LABOR 


Foundings.      Later,   when   conditions    become    favorable   for  its 

germination,  the  spore  may  form  a  new  filament  of  pond  scum. 

In  molds,  in  yeasts,  and  in  the  bacteria  we  also 
found  spores  could  be  formed  by  the  protoplasm 
of  the  plant  cutting  up  into  a  number  of  tiny 
spores.  These  spores  are  called  asexual  (without 
sex)  because  they  are  not  formed  by  the  union 
of  two  cells,  and  may  give  rise  to  other  tiny 
plants  like  themselves.  Still  other  plants,  mosses 
and  ferns,  give  rise  to  two  kinds  of  spores,  sexual 
and  asexual.  All  of  these  collectively  are  called 
spore  plants. 

Reproduction  in  Seed  Plants.  —  Another  great 
group  of  plants  we  have  studied,  plants  of  varied 
shapes  and  sizes,  produce 
seeds.  They  bear  flowers 
and  fruits. 

The  embryo  develops 
from  a  single  fertilized 
''  egg,"  growing  by  cell 
division   into  two,  four, 

eight,  and  a  constantly  increasing  number 

of  cells  until  after  a  time  a  baby  plant  is 

formed,  which  as  in  the  bean,  either  con- 
tains some  stored  food  to  give  it  a  start 

in  life,  or,  as  in  the  corn,  is  surrounded 

with  food  which  it  can  digest  and  absorb 

into  its  own  tiny  body.     We  have  seen 

that  these  young  plants  in  the  seed  are 

able  to  develop  when  conditions  are  favor- 
able.    Furthermore,   the   young  of  each 

kind  of  plant  will  eventually  develop  into 

the  kind  of  plant  its  parent  was  and  into 

no  other  kind.     Thus  the  plant  world  is 

divided  into  many  tribes  or  groups. 

Plants  are  placed  in  Groups.  —  If  we  plant  a  number  of  peas  so 

that  they  \vill  all  germinate  under  the  same  conditions  of  soil,  tem- 


The  formation  of 
spores  in  pond 
scum,  zs,  zygo- 
spore; /,  fusion 
in  progress. 


The  formation  and  growth  of 
a  plant  embryo.  1,  the 
«perm  and  egg  cell  uniting; 
2,  a  fertilized  egg;  3,  two 
cells  formed  by  division; 
4,  four  cells  formed  from 
two ;  5,  a  many-celled 
embryo;  6,  young  plant; 
H,  hypocotyl;  P,  plumule; 
C,  cotyledons. 


DIVISION  OF   LABOR 


175 


perature,  and  sunlight,  the 
seedlings  that  develop  will 
each  differ  one  from  an- 
other in  a  slight  degree.^ 
But  in  a  general  way  they 
will  have  many  characters 
in  common,  as  the  shape 
of  the  leaves,  the  posses- 
sion of  tendrils,  form  of 
the  flower  and  fruit.  A 
species  of  plants  or  animals 
is  a  group  of  individuals  so 
much  alike  in  their  char- 


A  colony  of  trilliums,  a  flowering  plant. 
(Photograph  by  W.  C.  Barbour.) 


acters  that  they  might  have  had  the  same  parents.     Individuals  of 
such  species  differ  slightly ;  for  no  two  individuals  are  exactly  alike. 

Species  are  grouped  to- 
gether in  a  larger  group 
called  a  genus.  For  ex- 
ample, many  kinds  of  peas 
—  the  wild  beach  peas,  the 
sweet  peas,  and  many 
others  —  are  all  grouped  in 
one  genus  (called  Lathyrus, 
or  vetchling)  because  they 
have  certain  structural 
characteristics  in  common. 
Plant  and  animal  genera 
are  brought  together  in  still 
larger  groups,  the  classifica- 
tion based  on  general  like- 
nesses in  structure.  Such 
groups  are  called,  as  they 
become  successively  larger, 


Rock  fern,  polypody.  Notice  the  underground 
stem  giving  off  roots  from  its  lower  surface, 
and  leaves  (C),  (S),  from  its  upper  surface. 


Family,  Order,  and  Class.     Thus  both  the  plant  and  animal  king- 
doms are  grouped  into  divisions,  the  smallest  of  which  contains 

1  Note  to  Teachers. — A  trip  to  the  Botanical  Garden  or  to  a  Museum  should 
be  taken  at  this  time. 


176 


PLANTS  CLASSIFIED 


individuals  very  much  alike ;  and  the  largest  of  which  contains 
very  many  groups  of  individuals,  the  groups  having  some  char- 
acters in  common.     This  is  called  a  system  of  classification. 

Classification  of  the  Plant  Kingdom. — The  entire  plant  king- 
dom has  been  divided  into  four  sub-kingdoms  by  botanists :  — 


1.  Spermatophytes. 


Angiosperms,  true  flowering  plants. 
Gymnosperms,  the  pines  and  their  allies. 

2.  Ptendophytes.     The  fern  plants  and  their  allies. 

3.  Bryophytes.         The  moss  plants  and  their  allies. 


Rockweed,  a  brown  algse,  showing  its  distribution  on  rocks  below  highwater  mark. 

4.  Thallophytes.  The  Thallophytes  form  two  groups :  the 
Algse  and  the  Fungi ;  the  algse  being  green,  while  the  fungi  have 
no  chlorophyll. 

The  extent  of  the  plant  kingdom  can  only  be  hinted  at ;  each 
year  new  species  are  added  to  the  lists.  There  are  about  110,000 
species  of  flowering  plants  and  nearly  as  many  flowerless  plants. 
The  latter  consist  of  over  3500  species  of  fernlike  plants,  some 
16,500  species  of  mosses,  over  5600  lichens  (plants  consisting  of  a 


DIVISION   OF   LABOR 


177 


partnership  between  algae  and  fungi),  approximately  55,000  species 
of  fungi,  and  about  16,000  species  of  algae. 

Development  of  a  Simple  Animal.  —  Many-celled  animals  are 
formed  in  much  the  same  way  as  are  many-celled  seed  plants.  A 
common  bath  sponge,  an  earthworm,  a  fish,  or  a  dog,  —  each  and 
all  of  them  begin  life  in  the  same 
manner.  In  a  many-celled  animal  the 
life  history  begins  with  a  single  cell, 
the  fertilized  egg.  As  in  the  flowering 
plant,  this  cell  has  been  formed  by 
the  union  of  two  other  cells,  a  tiny 
(usually  motile)  cell,  the  sperm,  and  a 
large  cell,  the  egg.  After  the  egg  is 
fertilized  by  a  sperm  cell,  it  splits  into 
two,  four,  eight,  and  sixteen  cells ; 
as  the  number  of  cells  increases,  a 
hollow  ball  of  cells  called  the  hlastula 
is  formed ;  later  this  ball  sinks  in  on 
one  side,  and  a  double-walled  cup  of 
cells,  now  called  a  gastrula,  results. 
Practically  all  animals  pass  through 
the  above  stages  in  their  development 
from  the  egg,  although  these  stages 
are  often  not  plain  to  see  because  of 
the  presence  of  food  material  (yolk) 
in  the  egg. 

In  animals  the  body  consists  of 
three  layers  of  cells :  those  of  the 
outside,  developed  from  the  outer 
layer  of  the  gastrula,  are  called  ecto- 
derm, which  later  gives  rise  to  the  skin,  nervous  system,  etc. ;  an 
inner  layer,  developed  from  the  inner  layer  of  the  gastrula,  the 
endoderm,  which  forms  the  lining  of  the  digestive  organs,  etc. ;  a 
middle  layer,  called  the  mesoderm,  lying  between  the  ectoderm 
and  the  endoderm,  is  also  found.  In  higher  animals  this  layer 
gives  rise  to  muscles,  the  skeleton,  and  parts  of  other  internal 
structures. 

HUNTER,    CIV.    BI. 12 


A  moss  plant.  (J,  the  luoss  body; 
S,  the  spore-bearing  stalk 
(fruiting  body). 


178 


DIVISION   OF  LABOR 


Physiological  Division  of  Labor.  —  If  we  compare  the  amoeba 
and  the  parama?fium,  we  find  the  latter  a  more  complex  organism 


Stages  in  the  development  of  a  fertilized  egg  into  the  gastrula  stage.     Read  your 
text,  then  draw  these  stages  and  name  each  stage. 


than  the  former.     An  amoeba  may  take  in  food  through  any  part 
of  the  body ;  the  paramoecium  has  a  definite  gullet ;  the  amoeba 

may  use  any  part  of  the 
body  for  locomotion;  the 
paramoecium  has  definite 
parts  of  the  cell,  the  cilia, 
fitted  for  this  work.  Since 
the  structure  of  the  para- 
moecium is  more  complex, 
we  say  that  it  is  a  ''  higher  " 
animal.  In  the  vorticella,  a 
still  more  complex  cell,  part 
of  the  cell  has  grown  out 
like  a  stalk,  has  become 
contractile,  and  acts  like 
muscle. 

As  we  look  higher  in  the 
scale    of    life,     we     inva- 

Photo^^ruph  of  a  living  vorticella,  showing  the  •    ui          fl     j       x,      .       pprtflin 

contractile    stalk  and    the  cilia  around  th ^  ^laDiy      nno      tnaL      certam 

mouth.    Compare  this  figure  with  that  of  the  parts  of    a  plant   or    animal 

paramoecium.      Which    cell    shows    greater  ,                i.      4.        j 

division  of  labor  ?  are   Set   apart    to    do   cer- 

tain work,  and  only  that 
work.  Just  as  in  a  community  of  people,  there  are  some 
men  who  do  rough  manual  work,  others  who  are  skilled  work- 
men, some  who  are  shopkeepers,  and  still  others  who  are  profes- 


DIVISION   OF   LABOR 


179 


sional  men,  so  among  plants 
and  animals,  wherever  col- 
lections of  cells  live  together 
to  form  an  organism,  there 
is  division  of  labor,  some 
cells  being  fitted  to  do 
one  kind  of  work,  while 
others  are  fitted  to  do  work 
of  another  sort.     This 


Different  forms  of  tissue  cells. 
C,  bone  making  cells ;  E,  epi- 
thelial cells;  F,  fat  cells;  L,  liver 
cells ;  M,  muscle  cell ;  i,  invol- 
untary; V,  voluntary;  A'',  nerve 
cell;  C B,  cell  body;  N.F.,  nerve 
fiber ;  T.B.,  nerve  endings ; 
W ,  colorless  blood  cells. 


Enlarged  lengthwise  section  of  the  hydra,  a 
very  simple  animal  which  shows  slight 
division  of  labor.  ba,  base  ;  b,  bud  ; 
m,  mouth;    ov,   ovary;    sp,  spermary. 

is    called    physiological    division    of 
labor. 

As  we  have  seen,  the  higher  plants 
are  made  up  of  a  vast  number  of  cells 
of  many  kinds.  Collections  of  cells 
alike  in  structure  and  performing  the 
same  function  we  have  called  a  tissue. 
Examples  of  animal  tissues  are  the 
highly  contractile  cells  set  apart  for 
movement,  rnuscles;  those  which 
cover  the  body  or  line  the  inner  parts 
of  organs,  the  skin,  or  epithelium ;  the 
cells  which  form  secretions  or  glands 
and  the  sensitive  cells  forming  the 
nervous  tissues. 

Frequently  several  tissues  have  cer- 


180 


DIVISION  OF  LABOR 


ri 


c.c. 


erid. 


TJli-S 


tain  functions  to  perform  in  conjunction  with  one  another  The 
arm  of  the  human  body  performs  movement.  To  do  this,  several 
tissues,  as  muscles,  nerves,  and  bones,  must  act  together.  A  col- 
lection of  tissues  performing  certain  work  we  call  an  organ. 

In  a  simple  animal  like  a  sponge,  division  of  labor  occurs  be- 
tween the  cells;  some  cells  which  line  the  pores  leading  inward 
create  a  current  of  water,  and  feed  upon  the  minute  organisms 
which  come  within  reach,  other  cells  build  the  skeleton  of  the 
sponge,  and  still  others  become  eggs  or  sperms.     In  higher  animals 

more  complicated  in  struc- 
ture and  in  which  the 
tissues  are  found  working 
together  to  form  organs, 
division  of  labor  is  much 
more  highly  specialized. 
In  the  human  arm,  an 
organ  fitted  for  certain 
movements,  think  of  the 
number  of  tissues  and  the 
complicated  actions  w^hich 
are    f)ossible.     The    most 

Part  of  a  sponge,   showing   how  cells  perform  extreme    division   of   labor 

division  of  labor,     ect,  ectoderm;  7nes,  meso-  .  •        j.u 

derm;    emd,    endoderm ;    c.c,    ciliated    cells,  IS    Seen     m    the    Orgamsm 

which  take  in  food  by  means  of  their  fla-  which   has   the   mOSt  COm- 
gellae  or  large  cilia  {fla),  ,  , .  ,  » 

plex  actions  to  periorm 
and  whose  organs  are  fitted  for  such  work,  for  there  the  cells  or 
tissues  which  do  the  particular  work  do  it  quickly  and  very  well. 

In  our  daily  life  in  a  town  or  city  we  see  division  of  labor  between 
individuals.  Such  division  of  labor  may  occur  among  other  ani- 
mals, as,  for  example,  bees  or  ants.  But  it  is  seen  at  its  highest 
in  a  great  city  or  in  a  large  business  or  industry.  In  the  stockyards 
of  Chicago,  division  of  labor  has  resulted  in  certain  men  performing 
but  a  single  movement  during  their  entire  day's  work,  but  this 
movement  repeated  so  many  times  in  a  day  has  resulted  in  wonder- 
ful accuracy  and  speed.     Thus  division  of  labor  obtains  its  end. 

Organs  and  Functions  Common  to  All  Animals.  —  The  same 
general  functions  performed  by  a  single  cell  are  performed  by  a 


DIVISION  OF  LABOR  181 

many-celled  animal.  But  in  the  many-celled  animals  the  various 
functions  of  the  single  cell  are  taken  up  by  the  organs.  In  a  com- 
plex organism,  like  man,  the  organs  and  the  functions  they  per- 
form may  be  briefly  given  as  follows :  — 

(1)  The  organs  of  food  taking :  food  may  be  taken  in  by  indi- 
vidual cells,  as  those  lining  the  pores  of  the  sponge,  or  definite 
parts  of  a  food  tube  may  be  set  apart  for  this  purpose,  as  the  mouth 
and  parts  which  place  food  in  the  mouth. 

(2)  The  organs  of  digestion :  the  food  tube  and  collections  of 
cells  which  form  the  glands  connected  with  it.  The  enzymes  in 
the  fluids  secreted  by  the  latter  change  the  foods  from  a  solid  form 
(usually  insoluble)  to  that  of  a  fluid.  Such  fluid  may  then  pass  by 
osmosis,  through  the  walls  of  the  food  tube  into  the  blood. 

(3)  The  organs  of  circulation :  the  tubes  through  which  the  blood, 
bearing  its  organic  foods  and  oxygen,  reaches  the  tissues  of  the 
body.  In  simple  animals,  as  the  sponge  and  hydra,  no  such  organs 
are  needed,  the  fluid  food  passing  from  cell  to  cell  by  osmosis. 

(4)  The  organs  of  respiration :  the  organs  in  which  the  blood 
receives  oxygen  and  gives  up  carbon  dioxide.  The  outer  layer  of 
the  body  serves  this  purpose  in  very  simple  animals ;  gills  or  lungs 
are  developed  in  more  complex  animals. 

(5)  The  organs  of  excretion :  such  as  the  kidneys  and  skin,  which 
pass  off  nitrogenous  and  other  waste  matters  from  the  body. 

(6)  The  organs  of  locomotion:  muscles  and  their  attachments 
and  connectives ;  namely,  tendons,  ligaments,  and  bones. 

(7)  The  organs  of  nervous  control:  the  central  nervous  system, 
which  has  control  of  coordinated  movement.  This  consists  of 
scattered  cells  in  low  forms  of  life ;  such  cells  are  collected  into 
groups  and  connected  with  each  other  in  higher  animals. 

(8)  The  organs  of  sense:  collections  of  cells  having  to  do  with 
the  reception  and  transmission  of  sight,  hearing,  smell,  taste,  touch, 
pressure,  and  temperature  sensations. 

(9)  The  organs  of  reproduction :  the  sperm  and  egg-forming 
organs. 

Almost  all  animals  have  the  functions  mentioned  above.  In 
most,  the  various  organs  mentioned  are  more  or  less  developed, 
although  in  the  simpler  forms  of  animal  life  some  of  the  organs 


182 


ANIMALS  CLASSIFIED 


mentioned  above  are  either  very  poorly  developed  or  entirely 
lacking.  But  in  the  so-called  "  higher "  animals  each  of  the 
above-named  functions  is  assigned  to  a  certain  organ  or  group  of 
organs.  The  work  is  done  better  and  more  quickly  than  in  the 
"  lower  "  animals.  Division  of  labor  is  thus  a  guide  in  helping 
us  to  determine  the  place  of  animals  in  the  groups  that  exist  on  the 
earth. 

The  Animal  Series.  —  We  have  found  that  a  one-celled  animal 
can  perform  certain  functions  in  a  rather  crude  manner.     Man 

can  perform  these  same  functions 
in  an  extremely  efficient  manner. 
Division  of  labor  is  well  worked 
out,  extreme  complexity  of  struc- 
ture is  seen.  Between  these  two 
extremes  are  a  great  many  groups 
of  animals  which  can  be  arranged 
more  or  less  as  a  series,  showing 
the  gradual  evolution  or  develop- 
ment of  life  on  the  earth.  It 
will  be  the  purpose  of  the  follow- 
ing pages  to  show  the  chief  char- 
acteristics of  the  great  groups  of 
the  animal  kingdom. 
I.  Protozoa.  —  Animals  composed  of  a  single  cell,  reproducing 
by  cell  division. 

The  following  are  the  principal  classes  of  Protozoa,  examples  of  which  we  may 

have  seen  or  read  about :  — 

Class  I.  Rhizopoda  (Greek  for  root-footed).  Having  no  fixed  form,  with  pseudo- 
podia.  Either  naked  as  Amoeba  or  building  limy  (Foraminifera)  or  glasslike 
skeletons  (Radiolaria) . 

Class  II.  Infusoria  {in  infusions).  Usually  active  ciliated  Protozoa.  Examples, 
Paramcecium,  Vorticella. 

Class  III.  Sporozoa  (spore  animals).  Parasitic  and  usually  nonactive.  Exam- 
ple, Plasmodium  malarioe. 


The  giasslike  skeleton  of  h  radiolarian, 
a  protozoan.  (From  model  at  Ameri- 
can Museum  of  Natural  History.) 


II.  Sponges.  —  Because  the  body  contains  many  pores  through 
which  water  bearing  food  particles  enters,  these  animals  are  called 
Porifera.  They  are  classed  according  to  the  skeleton  they  possess 
into   limy,  glasslike,  and   horny  fiber  sponges.     The  latter  are 


ANIMALS   CLASSIFIED 


183 


A  horny  fiber  sponge.     Notice  that  it  is  a 
colony.     One  fourth  natural  size. 


the  sponges  of  commerce. 
With  but  few  exceptions 
sponges  Hve  in  salt  water 
and  are  never  free  swim- 
ming. 

III.  Coelenterates.  — 
The  hydra  and  its  salt- 
water allies,  the  jellyfish, 
hydroids,  and  corals,  be- 
long to  a  group  of  animals 
known  as  the  Coelenterata. 
The  word  '^  coelenterate" 
(coelom  =  body  cavity,  en- 
ter on  =  food  tube)  explains 

the  structure  of  the  group.  They  are  animals  in  which  the  real 
body  cavity  is  lacking,  the  animal  in  its  simplest  form  being  little 
more  than  a  bag.  Some  examples  are  the  hydra,  shown  on  page 
179,  salt-water  forms  known  as  hydroids,  colonial  forms  which  have 

part  of  their  life  free  smm- 
ming  as  jellyfish ;  sea  anemones 
and  coral  polyps,  tiny  colonial 
hydra  like  forms  which  build 
a  living  or  secreted  covering. 

IV.  Worms.  —  The  worm- 
like animals  are  grouped  into 
flatworms,  roundworms,  and 
segmented  or  jointed  worms. 

(a)  Flatworms  are  somet  imes 

parasitic,  examples  being  the 

tapeworm     and     liver     fluke. 

They  are  usually  small,  ribbon- 

or  leaf-like  and  flat  and  live  in 

water. 

(6)  Roundworms,  minute   threadlike   creatures,  are  not   often 

seen  by  the  city  girl  or  boy.     Vinegar  eels,  the  horsehair  worm, 

the  pork  worm  or  trichina  and  the  dread  hookworm  are  examples. 

(c)  Segmented  worms  are  long,  jointed  creatures  composed  of 


Sea  anemones.  One  half  natural  size.  The 
right  hand  specimen  is  expanded  and 
shows  the  mouth  surrounded  by  the 
tentacles.  The  left  hand  specimen  is 
contracted.  (From  model  at  the  Ameri- 
can Museum  of  Natural  History.) 


184 


ANIMALS  CLASSIFIED 


body  rings  or  segments.  Examples  are  the  earth- 
worm, the  sandworm  (known  to  New  York  boya 
as  the  fishworm),  and  the  leeches  or  bloodsuckers. 


A  jointed  worm. 
The  sandworm. 
Slightly  reduced. 


^^^^^^^^^^^^^^^^^^^^^V^v'^^^^^^^^^^^^^^^^^^^^^^^^^H 

^■1 

^^^^^^^^^^^f  ( '^^^^^^^^^^^^^^1 

^^^H 

^^^^^^^^^^^^^^'< .' ;  ^^^^^^^^^^^^^1 

^^H 

F^^Br  vim 

,,J3H 

^^g^^^^m 

BI^B 

1 

^^^^E^^^^^^^^^^^H 

^1 

The  common  starfish  seen  from  below  to  show 
the  tube  feet.     About  one  half  natural  size. 


V.  Echinoderms.  —  These    are    spiny-skinned    animals,   which 
live  in  salt  water.     They  are  still  more  complicated  in  structure 


The  crayfish,  a  crustacean.  A,  antenna;  AI,  mouth;  E,  compound  stalked  eye; 
Ch,  pincher  claw;  C.P.,  cephalothorax ;  Ab,  abdomen;  C.F.,  caudal  fin.  A 
Uttle  reduced. 


ANIMALS   CLASSIFIED 


185 


A  common  snail,  a 
mollusk.  (From  a 
photograph  by 
Davison.) 


than  the  worms  and  may  be  known  by  the  spines  in  their  skin. 
They  show  radial  symmetry.     Starfish  or  sea  urchins  are  examples. 

VI.  Arthropods.  —  These  animals  are  distinguished  by  havmg 
jointed  body  and  legs.  They  form  two  great  groups.  The  higher 
forms  of  the  Crustacea  have  only  two  regions  in  the  body,  a  fused 
head  and  thorax,  called  the  cephalothorax,  and  an  abdominal 
region.  A  second  group  is  the  Inseda,  of  which  we  know  some- 
thing already.  Crustacea  breathe  by  means 
of  gills,  which  are  structures  for  taking  oxygen 
out  of  the  water,  while  adult  insects  breathe 
through  air  tubes  called  trachea. 

Two  smaller  groups  of  arthropods  also  exist, 
the  Arachnida,  consisting  of  spiders,  scorpions, 
ticks,  and  mites,  and  the  Myriapoda,  examples 
being  the  "  thousand  leggers  "  found  in  some 
city  houses. 

VII.  Mollusca.  —  Another  large  group  is  the 
Mollusca.     This  phylum  gets  its  name  from 
the   soft,    unsegmented   body    {mollis  =  soft). 
Mollusks  usually  have  a  shell,  which  may  be  of  one  piece,  as  a 
snail,  or  two  pieces  or  valves,  as  the  clam  or  oyster. 

VIII.  The  Vertebrates.  —  All  of  the  animals  we  have  studied 
thus  far  agree  in  having  whatever  skeleton  or  hard  parts  they 
possess  on  the  outside  of  the  body.  Collectively,  they  are  called 
Invertebrates.     This  exoskeleton  differs  from  the  main  or  axial 

skeleton  of  the  higher 
animals,  the  latter  be- 
ing inside  of  the  body. 
The  exoskeleton  is 
dead,  being  secreted 
by  the  cells  lining  the 
body,  while  the  endo- 
skeleton  is,  in  part  at 
least,  alive  and  is 
capable  of  growth,  e.g. 
a  broken  arm  or  log 
The  skeleton  of  a  dog ;  a  typical  vertebrate.  bone     will     groW     tO- 


186 


ANIMALS   CLASSIFIED 


get  her.  But  a  man  has  certain  parts  of  the  skeleton,  as  nails  or 
hair,  formed  by  the  skin  and  in  addition  possesses  inside  bones  to 
which  the  muscles  are  attached.  Some  of  the  bones  are  arranged 
in  a  flexil)le  column  in  the  dorsal  (the  back)  side  of  the  body. 
This  vertebral  column,  as  it  is  called,  is  distinctive  of  all  vertebrates. 
Within  its  bony  protection  lies  the  delicate  central  nervous  system, 
and  to  this  column  are  attached  the  big  bones  of  the  legs  and 
arms.  The  vertebrate  animals  deserve  more  of  our  attention  than 
other  forms  of  life  because  man  himself  is  a  vertebrate. 


The  sand  shark,  an  elasmobranch.     Note  the  sUts  leading  from  the  gills.     (From 
a  photograph  loaned  by  the  American  Museum  of  Natural  History.) 

Five  groups  or  classes  of  vertebrates  exist.  Fishes,  Amphibians, 
Reptiles,  Birds,  and  Mammals.  Let  us  see  how  to  distinguish  one 
class  from  another. 

Fishes.  —  Fishes  are  familiar  animals  to  most  of  us.  We  know 
that  they  live  in  the  water,  have  a  backbone,  and  that  they  have 
fins.  They  breathe  by  means  of  gills,  delicate  organs  fitted  for 
taking  oxygen  out  of  the  water.  The  heart  has  two  chambers,  an 
auricle  and  a  ventricle.     They  have  a  skin  in  which  are  glands 


The  sturgeon,  a  ganoid  fish. 


ANIMALS  CLASSIFIED 


187 


secreting  mucus,  a  slimy  substance  which  helps  them  go  through 
the  water  easily.     They  usually  lay  very  many  eggs. 

Classification  of  Fishes 

Order  I.     The  ElasmobrancJis.     Fishes  which  have  a  soft  skeleton  made  of  cartilage 

and  exposed  gill  slits.     Examples  :  sharks,  skates,  and  rays. 
Order  II.     The  Ganoids.    Fishes  which  once  were  very  numerous  on  the  earth,  but 

which  are  now  almost  extinct.     They  are  protected  by  platelike  scales.     Ex- 
amples :  gars,  sturgeon,  and  bowfin. 
Order  III.     The  Teleosts,  or  Bony  Fishes. 

They  compose  95  per  cent  of  all  living 

fishes.     In  this  group  the  skeleton  is 

bony,   the   gills   are    protected   by  an 

operculum,  and  the  eggs  are  numerous. 

Most  of  our  common  food  fishes  belong 

to  this  class. 
Order  IV.     The  Dipnoi,  or  Lung  Fishes. 

This  is  a  very  small  group.     In  many  A  bony  fish. 

respects  they  are  more  like  amphibians 

than  fishes,  the  swim  bladder  being  used  as  a  lung.     They  live  in  tropical 

Africa,  South  America,  and  Australia,  inhabiting  the  rivers  and  lakes  there. 

Characteristics  of  Amphibia.  —  The  frog  belongs  to  the  class  of 
vertebrates  known  as  Amphibia.  As  the  name  indicates  {amphi, 
both,  and  bia,  life),  members  of  this  group  live  both  in  water  and 
on  land.  In  the  earlier  stages  of  their  development  they  take 
oxygen  into  the  blood  by  means  of  gills.  When  adult,  however, 
they  breathe  by  means  of  lungs.  At  all  times,  but  especially 
during  the  winter,  the  skin  serves  as  a  breathing  organ.     The 


Newt.     (From  a  photograph  loaned  by  the  American  Museum  of  Natural 

History.)     About  natural  size. 

skin  is  soft  and  unprotected  by  bony  plates  or  scales.  The  heart 
has  three  chambers,  two  auricles  and  one  ventricle.  Most  am- 
phibians undergo  a  complete  metamorphosis,  or  change  of  form, 
the  young  being  unlike  the  adults. 


188 


ANIMALS   CLASSIFIED 


Classification  of  Amphibia 

Order  I.  Urodela.  Amphibia  having  usually  poorly  developed  appendages. 
Tail  persistent  throu<>;h  life.     Examples  :    iiiud  puppy,  newt,  salamander. 

Ordkr  II.  Anura.  Tailless  Amphibia,  which  undergo  a  metamorphosis,  breath- 
ing Ijy  gills  in  larval  state,  by  lungs  in  adult  state.     Examples  :   toad  and  frog. 

Characteristics  of  Reptilia. 
—  These  animals  are  char- 
acterized by  having  scales 
developed  from  the  skin.  In 
the  turtle  they  have  become 
bony  and  are  connected  with 
the  internal  skeleton.  Rep- 
tiles always  breathe  by  means 
of  lungs,  differing  in  this 
respect  from  the  amphibians. 
They  show  their  distant  re- 
lationship to  birds  in  that 
their  large  eggs  are  incased 
in  a  leathery,  limy  shell. 


P^^ 

(»i.'.  -. '^'^>'^  v^^ 

■'^'  '^' '' v^&"^/ii 

^^^^^^St^^^9r  : 

The  leopard  frog,  an  amphibian. 


Classification  of  Reptiles 


Order  I.     Chelonia  (turtles  and  tortoises), 
in   bony   case.     No   teeth   or    sternum 
turtle,  box  tortoise. 

Order  II.  Lacertilia  (lizards).  Body 
covered  with  scales,  usually  having 
two-paired  appendages.  Breathe 
by  lungs.  Examples  :  fence  lizard, 
horned  toad. 


Flattened  reptiles  with  body  inclosed 
(breastbone).     Examples:     snapping 


Box  tortoise,  a  land  reptile.  (From 
photograph  loaned  by  the  Ameri- 
can Museum  of  Natural  History.) 
About  one  fourth  natural  size. 


The  gila  monster,  a 
poisonous  lizard. 
About  one  twelfth 
natural  size. 


ANIMALS   CLASSIFIED 


189 


Order  III.  Ophidia  (snakes).  Body 
elongated,  covered  with  scales.  No 
limbs  present.  Examples  :  garter 
snake,  rattlesnake. 

Order  IV.  Crocodilia.  Fresh-water 
reptiles  with  elongated  body  and 
bony  scales  on  skin.  Two-paired 
limbs.  Examples  :  alligator,  crocodile. 


The  common  garter  snake.     Reduced 
to  about  one  tenth  natural  size. 


Birds.  —  Birds  among  all  other 
animals  are  known  by  their  cov- 
ering of  feathers  and  the  presence  of  wings.     The  feathers  are  de- 
veloped from  the  skin.     These  aid  in  flight,  and  protect  the  body 
from  the  cold. 


Adaptations  in  the  bills  of  birds.  Could  we  tell  anything  about  the  food  of  a  bird 
from  its  bill  ?  Do  these  birds  all  get  their  food  in  the  same  manner  ?  Do 
they  all  eat  the  same  kind  of  food  ? 


The  form  of  the  bill  in  particular  shows  adaptation  to  a  wonder- 
ful degree.  A  duck  has  a  flat  bill  for  pushing  through  the  mud  and 
straining  out  the  food  ;  a  bird  of  prey  has  a  curved  or  hooked  beak 
for  tearing ;  the  woodpecker  has  a  sharp,  straight  bill  for  piercing 
the  bark  of  trees  in  search  of  the  insect  larvae  which  are  hidden 
underneath.     Birds  do  not  have  teeth. 


190 


ANIMALS   CLASSIFIED 


The  rate  of  respiration,  of  heartbeat,  and  the  body  temperature 
are  all  higher  in  the  bird  than  in  man.  Man  breathes  from  twelve 
to  fourteen  times  per  minute.  Birds  breathe  from  twenty  to  sixty 
times  a  minute.  Because  of  the  increased  activity  of  a  bird, 
there  comes  a  necessity  for  a  greater  and  more  rapid  supply  of 
oxygen,  an  increased  blood  supply  to  carry  the  material  to  be 
used  u\)  in  the  release  of  energy,  and  a  means  of  rapid  excretion 
of  the  wastes  resulting  from  the  process  of  oxidation.     Birds  are 


Common  torn  and  young,  showing  nesting  and  feeding  habits.     (From  group 
at  American  Museum  of  Natural  History.) 

large  eaters,  and  the  digestive  tract  is  fitted  to  digest  the  food 
quickly,  by  having  a  large  crop  in  which  food  may  be  stored  in  a 
much  softened  condition.  As  soon  as  the  food  is  part  of  the  blood, 
it  may  be  sent  rapidly  to  the  places  where  it  is  needed,  by  means 
of  the  large  four-chambered  heart  and  large  blood  vessels. 

The  high  temperature  of  the  bird  is  a  direct  result  of  this  rapid 
oxidation ;  furthermore,  the  feathers  and  the  oily  skin  form  an 
insulation  which  does  not  readily  permit  of  the  escape  of  heat. 
This  insulating  cover  is  of  much  use  to  the  bird  in  its  flights  at 


ANIMALS   CLASSIFIED 


191 


high  altitudes,  where  the  temperature  is  often  very  low.     Birds 
lay  eggs  and  usually  care  for  their  young. 


Examples : 


Classification  of  Birds 

Order  I.   Cursores.     Running    birds    with    no    keeled    breastbone. 

ostrich,  cassowary. 
Order  II.   Passeres.    Perching  birds ; 

three  toes  in  front,  one  behind. 

Over  one  half  of  all   species  of 

birds  are  included  in  this  order. 

Examples  :      sparrow,      thrush, 

swallow. 
Order  III.     Gallince.     Strong    legs ; 

feet  adapted  to  scratching.   Beak 

stout.     Examples :    jungle   fowl, 

grouse,  quail,  domestic  fowl. 
Order  IV.    Raptores.    Birds  of  prey. 

Hooked    beak.      Strong    claws. 

Examples :  eagle,  hawk,  owl. 
Order    V.       Grallatores.       Waders. 

Long  neck,  beak,  and  legs.     Ex- 
amples :  snipe,  crane,  heron. 
Order  VI.    Natatores.      Divers   and 

swimmers.        Legs     short,     toes 

webbed.     Examples  :  gull,  duck, 

albatross. 
Order  VII.    Columbince.    Like  Gal- 

linse,  but  with  weaker  legs.     Ex- 
amples :  dove,  pigeon. 
Order  VIII.     Pici.      Woodpeckers. 

Two    toes    point    forward,    two 

backward,    and    adaptation    for 

climbing.     Long,  strong  bill. 
Order  IX.   Psittaci.    Parrots,  hooked  beak  and  fleshy  tongue. 
Order  X.   Coccyges.      Climbing   birds,  with   powerful    beak.      Examples :     king- 
fisher, toucan,  and  cuckoo. 
Order  XL   Macrochires.      Birds  having    long-pointed  wings,  without   scales    on 

metatarsus.     Examples  :  swift,  humming  bird,  and  goatsucker. 

Mammals.  —  Dogs  and  cats,  sheep  and  pigs,  horses  and  cows, 
all  of  our  domestic  animals  (and  man  himself)  have  characters  of 
structure  which  cause  them  to  be  classed  as  mammals.  They,  like 
some  other  vertebrates,  have  lungs  and  warm  blood.  Tliey  also 
have  a  hairy  covering  and  bear  young  developed  to  a  form  sirnilar  to 
their  own,^  and  nurse  them  with  milk  secreted  by  glands  known 
as  the  mammary  glands  ;   hence  the  term  ''  mammal." 

^  With  the  exception  of  the  mouotremes. 


African  ostrich,  one  of  the  largest 
living  birds. 


192 


EVOLUTION 


The  bisoD,  an  almost  extinct  mammal. 


Adaptations  in  Mammalia.  —  Of  the  thirty-five  hundred  species, 
most  inhabit  continents;  a  few  species  are  found  on  different  islands, 
and  some,  as  the  whale,  inhabit  the  ocean.     They  vary  in  size  from 
the  whale  and  the  elephant  to  tiny  shrew  mice  and  moles.     Adapta- 
tions to  different  habitat 
and  methods  of  life  abound ; 
the  seal   and  whale  have 
the    limbs    modified    into 
flippers,     the     sloth     and 
squirrel  have  limbs  pecul- 
iarly adapted  to  climbing, 
while   the   bats   have   the 
fore    limbs    modeled    for 
flight. 

Lowest     Mammals.  —  The 
lowest  are  the  monotremes, 
animals  which  lay  eggs  like 
the  birds,  although  they  are 
provided  with  hairy  covering  like  other  mammals.     Such  are  the  Aus- 
tralian spiny  anteater  and  the  duck  mole. 

All  other  mammals  bring  forth  their  j^oung  developed  to  a  form  simi- 
lar to  their  own.  The  kangaroo  and  opossum,  however,  are  provided 
with  a  pouch  on  the  under  side  of  the  body  in  which  the  very  immature, 
blind,  and  helpless  young  are  nourished  until  they  are  able  to  care  for 
themselves.  These  pouched  animals  are  called  marsupials. 
The  other  mammals  may  be  briefly  classified  as  follows :  — 

Classification  of  Higher  Mammals 

Order  I.  Edentata.  Toothless  or  with  very  simple  teeth.  Examples:  anteater, 
sloth,  armadillo. 

Order  II.  Rodentia.  Incisor  teeth  chisel-shaped,  usually  two  above  and  two 
below.     Examples  :  beaver,  rat,  porcupine,  rabbit,  squirrel. 

Order  III.   Cetacea.     Adapted  to  marine  life.     Examples  :  whale,  porpoise. 

Order  IV.  Ungulata.  Hoofs,  teeth  adapted  for  grinding.  Examples :  (a)  odd- 
toed,  horse,  rhinoceros,  tapir ;    (6)  even-toed,  ox,  pig,  sheep,  deer. 

Order  V.  Carnivora.  Long  canine  teeth,  sharp  and  long  claws.  Examples  :  dog, 
cat,  lion,  bear,  seal,  and  sea  lion. 

Order  VI.  Insectivora.    Example  :  mole. 

Order  VII.  Cheiroptera.   Fore  limbs  adapted  to  flight,  teeth  pointed.   Example:  bat. 

Order  VIII.  Primates.  Erect  or  nearly  so,  fore  appendage  provided  with  hand. 
Examples  :  monkey,  ape,  man. 


EVOLUTION 


193 


Increasing  Complexity  of  Structure  and  of  Habits  in  Plants  and 
Animals.  —  In  our  study  of  biology  so  far  we  have  attempted  to 
get  some  notion  of  the  various  factors  which  act  upon  living  things. 
We  have  seen  how  plants  and  animals  interact  upon  each  other. 
We  have  learned  something  about  the  various  physiological  pro- 
cesses of  plants  and  animals,  and  have  found  them  to  be  in  many 
respects  identical.  We  have  found  grades  of  complexity  in  plants 
from  the  one-celled  plant,  bacterium  or  pleurococcus,  to  the  com- 
plicated  flowering   plants   of   considerable   size   and   with   many 


=Musnei>^anctrIt'T-t:e/t3i 


The  geological  history  of  the  horse.     (After  Mathews,  in  the  American  Museum 
of  Natural  History.)     Ask  your  teacher  to  explain  this  diagram. 

organs.  So  in  animal  life,  from  the  Protozoa  upward,  there  is 
constant  change,  and  the  change  is  toward  greater  complexity  of 
structure  and  functions.  An  insect  is  a  higher  type  of  life  than  a 
protozoan,  because  its  structure  is  more  complex  and  it  can  per- 
form its  work  with  more  ease  and  accuracy.  A  fish  is  a  higher 
type  of  animal  than  the  insect  for  these  same  reasons,  and  also  for 
another.  The  fish  has  an  internal  skeleton  which  forms  a  pointed 
column  of  bones  on  the  dorsal  side  (the  back)  of  the  animal.  It  is 
a  vertebrate  animal. 

HUNTER,  CIV    BI. 1? 


194 


EVOLUTION 


Mammals 


"Birds 
13000 


Reptiles 
03500 

Amphibians 
/l400 


Fishes 
13000 


The  Doctrine  of  Evolution. — We  have  now  learned  that  animal 
forms  may  be  arranged  so  as  to  begin  with  very  simple  one-celled 
forms  and  culminate  with  a  group  which  contains  man  himself. 
This  arrangement  is  called  the  evolutionary  series.    Evolution  means 

change,  and  these  groups 
are  believed  by  scientists 
to  represent  stages  in  com- 
plexity of  development  of 
life  on  the  earth.  Geology 
teaches  that  millions  of 
years  ago,  life  upon  the 
earth  was  very  simple, 
and  that  gradually  more 
and  more  complex  forms 
of  life  appeared,  as  the 
rocks  formed  latest  in  time 
show  the  most  highly  de- 
veloped forms  of  animal 
life.  The  great  English 
scientist,  Charles  Darwin, 
from  this  and  other  evi- 
dence, explained  the  theory 
of  evolution.  This  is  the 
belief  that  simple  forms  of  life  on  the  earth  slowly  and  gradually 
gave  rise  to  those  more  complex  and  that  thus  ultimately  the  most 
complex  forms  came  into  existence. 

The    Number   of   Animal    Species.  —  Over   500,000   species   of 
animals  are  known  to  exist  to-day,  as  the  following  table  showSc 


Crustacea  f  16  000 


Myrh 

4000\fooO. 

Annelids ' 

Echinoderms^^^^f^^\  J 

Flat  ^ormsSOQLj^ 

Sponges 

'       "^2500/ 


Coelenterates 
4500 

Protozoa  8000 


The  evolutionary  tree.  Modified  from  Gal- 
loway. Copy  this  diagram  in  your  note- 
book.    Explain  it  as  well  as  you  can. 


Protozoa 

Sponges 

Coelenterates 

Echinoderms 

Flatworms 

Roundworms 

Annelids 

Insects    .     . 

Myriapods  . 


8,000 

Arachnids   . 

2,500 

Crustaceans 

4,500 

MoUusks     . 

4,000 

Fishes     .     . 

5,000 

Amphibians 

1,500 

Reptiles 

4,000 

Birds      .     . 

360,000 

Mammals    . 

2,000 

Total     . 

16,000 

16,000 

61,000 

13,000 

1,400 

3,500 

13,000 

3,500 

518,900 


EVOLUTION  195 

Man's  Place  in  Nature.  —  Although  we  know  that  man  is 
separated  mentally  by  a  wide  gap  from  all  other  animals,  in  our 
study  of  physiology  we  must  ask  where  we  are  to  place  man.  If  we 
attempt  to  classify  man,  we  see  at  once  he  must  be  placed  with 
the  vertebrate  animals  because  of  his  possession  of  a  vertebral 
column.  Evidently,  too,  he  is  a  mammal,  because  the  young  are 
nourished  by  milk  secreted  by  the  mother  and  because  his  body 
has  at  least  a  partial  covering  of  hair.  Anatomically  we  find  that 
we  must  place  man  with  the  apelike  mammals,  because  of  these 
numerous  points  of  structural  likeness.  The  group  of  mammals 
which  includes  the  monkeys,  apes,  and  man  we  call  the  primates. 

Although  anatomically  there  is  a  greater  difference  between 
the  lowest  type  of  monkey  and  the  highest  type  of  ape  than  there 
is  between  the  highest  type  of  ape  and  the  lowest  savage,  yet  there 
is  an  immense  mental  gap  between  monkey  and  man. 

Instincts.  —  Mammals  are  considered  the  highest  of  vertebrate 
animals,  not  only  because  of  their  complicated  structure,  but  be- 
cause their  instincts  are  so  well  developed.  Monkeys  certainly 
seem  to  have  many  of  the  mental  attributes  of  man. 

Professor  Thorndike  of  Columbia  University  sums  up  their  habits 
of  learning  as  follows  :  — 

"  In  their  method  of  learning,  although  monkeys  do  not  reach  the 
human  stage  of  a  rich  life  of  ideas,  yet  they  carry  the  animal  method  of 
learning,  by  the  selection  of  impulses  and  association  of  them  with  differ- 
ent sense-impressions,  to  a  point  beyond  that  reached  by  any  other  of 
the  lower  animals.  In  this,  too,  they  resemble  man ;  for  he  differs  from 
the  lower  animals  not  only  in  the  possession  of  a  new  sort  of  intelligence, 
but  also  in  the  tremendous  extension  of  that  sort  which  he  has  in  common 
with  them.  A  fish  learns  slowly  a  few  simple  habits.  Man  learns  quickly 
an  infinitude  of  habits  that  may  be  highly  complex.  Dogs  and  cats  learn 
more  than  the  fish,  while  monkeys  learn  more  than  the3^  In  the  number 
of  things  he  learns,  the  complex  habits  he  can  form,  the  variety  of  lines 
along  which  he  can  learn  them,  and  in  their  permanence  when  once  formed, 
the  monkey  justifies  his  inclusion  with  man  in  a  separate  mental  genus." 

Evolution  of  Man.  —  Undoubtedly  there  once  lived  upon  the 
earth  races  of  men  who  were  much  lower  in  their  mental  organiza- 
tion than  the  present  inhabitants.     If  we  follow  the  early  history 


196  EVOLUTION 

of  man  upon  the  earth,  we  find  that  at  first  he  must  have  been 
Uttle  better  than  one  of  the  lower  animals.  He  was  a  nomad, 
wandering  from  place  to  place,  feeding  upon  whatever  living  things 
he  could  kill  with,  his  hands.  Gradually  he  must  have  learned  to 
use  weapons,  and  thus  kill  his  prey,  first  using  rough  stone  im- 
plements for  this  purpose.  As  man  became  more  civilized,  im- 
plements of  bronze  and  of  iron  were  used.  About  this  time  the 
subjugation  and  domestication  of  animals  began  to  take  place. 
Man  then  began  to  cultivate  the  fields,  and  to  have  a  fixed  place 
of  abode  other  than  a  cave.  The  beginnings  of  civilization  were 
long  ago,  but  even  to-day  the  earth  is  not  entirely  civilized. 

The  Races  of  Man.  —  At  the  present  time  there  exist  upon  the 
earth  five  races  or  varieties  of  man,  each  very  different  from  the 
other  in  instincts,  social  customs,  and,  to  an  extent,  in  structure. 
These  are  the  Ethiopian  or  negro  type,  originating  in  Africa ;  the 
Malay  or  brown  race,  from  the  islands  of  the  Pacific ;  the  Amer- 
ican Indian ;  the  Mongolian  or  yellow  race,  including  the  natives 
of  China,  Japan,  and  the  Eskimos ;  and  finally,  the  highest  type 
of  all,  the  Caucasians,  represented  by  the  civilized  white  in- 
habitants of  Europe  and  America. 

Reference  Books 
elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology,  American  Book  Company. 

Bulletin  of  U.S.  Department  of  Agriculture,  Division  of  Biological  Survey,  Nos.  1, 

6,  13,  17. 
Davison,  Practical  Zoology.     American  Book  Company. 

Ditmars,  The  Reptiles  of  New  York.     Guide  Leaflet  20.     Amer.  Mus.  of  Nat.  History. 
Sharpe,  A  Laboratory  Manual  in  Biology,  pp.  140-150,  American  Book  Company. 
Walker,  Our  Birds  and  Their  Nestlings.     American  Book  Company. 
Walter,  H.  E.  and  H.  A.,  Wild  Birds  in  City  Parks.     Published  by  authors. 

ADVANCED 

Apgar,  Birds  of  the  United  States.     American  Book  Company. 

Beebe,  The  Bird.     Henry  Holt  and  Company. 

Ditmars,  The  Reptile  Book.     Doubleday,  Page  and  Company. 

Hegner,  Zoology.     The  Macmillan  Company. 

Hornaday,  American  Natural  History. 

Jordan  and  Evermann,  Food  and  Game  Fishes.     Doubleday,  Page  and  Company. 

Parker  and  Haswell,  Textbook  of  Zoology.     The  Macmillan  Company. 

Riverside  Natural  History.     Houghton,  Mifflin  and  Company. 

Weed  and  Dearborn,  Relation  of  Birds  to  Man.     Lippincott. 


XV.  THE  ECONOMIC  IMPORTANCE  OF  ANIMALS 

rroblems.  —  I,   To  deterinine  the  uses  of  animals. 
{a)  Indirectly  as  food. 

(b)  Directly  as  food. 

(c)  As  doinesticated,  animals, 
id)  For  clothing. 

(e)    Other  direct  economic  uses. 

(/)  Destj^uction  of  harmful  plants  and  animals. 

II*   To  determine  the  harm  done  hy  animals. 
ia)  Animals  destructive  to  those  used  for  food. 

(b)  Animals  harmful  to  crops  and  gardens. 

(c)  Animals  harmful  to  fruit  and  forest  trees. 

(d)  Animals  destructive  to  stored  food  or  clothing. 

(e)  Animals  indirectly  or  directly  responsible  for  disease. 

Laboratory  Suggestions 

Inasmuch  as  this  work  is  planned  for  the  winter  months  the  laboratory 
side  must  be  largely  museum  and  reference  work.  It  is  to  be  expected 
that  the  teacher  will  wish  to  refer  to  much  of  this  work  at  the  time  work  is 
done  on  a  given  group.  But  it  is  pedagogically  desirable  that  the  work  as 
planned  should  be  varied.  Interest  is  thus  held.  Outlines  prepared  by 
the  teacher  to  be  filled  in  by  the  student  are  desirable  because  they  lead 
the  pupil  to  individual  selection  of  what  seems  to  him  as  important  mate- 
rial. Opportunity  should  be  given  for  laboratory  exercises  based  on 
original  sources.  The  pupils  should  be  made  to  use  reports  of  the  U.  S. 
Department  of  Agriculture,  the  Biological  Survey,  various  States  Reports, 
and  others. 

Special  home  laboratory  reports  may  be  well  made  at  this  time,  for 
example  :  determination  at  a  local  fish  market^  of  the  fish  that  are  cheap 
and  fresh  at  a  given  time.  Have  the  students  give  reasons  for  this. 
Study  conditions  in  the  meat  market  in  a  similar  manner.  Other  local 
food  conditions  may  also  be  studied  first  hand. 

197 


98    THE  ECONOMIC  IMPORTANCE  OF  ANIMALS 


USES   OF  ANIMALS 

Indirect  Use  as  Food.  —  Just  as  plants  form  the  food  of  ani- 
mals, so  some  animals  are  food  for  others.  Man  may  make  use 
of  such  food  directly  or  indirectly.  Many  mollusks,  as  the  bar- 
nacle and  mussel,  are  eaten  by  fishes.     Other  fish  live  upon  tiny 

organisms,  water  fleas  and  other  small 
crustaceans.  These  in  turn  feed  upon 
still  smaller  animals,  and  we  may  go 
back  and  back  until  finally  we  come 
to  the  Protozoa  and  one-celled  water 
plants  as  an  ultimate  source  of  food. 

Direct  Use  as  Food.  Lower  Forms. 
—  The  forms  of  life  lower  than  the 
Crustacea  are  of  little  use  directly  as 
food,  although  the  Chinese  are  very 
fond  of  one  of  the  Echinoderms,  a 
holothurian. 

Crustacea  as  Food.  —  Crustaceans, 
however,  are  of  considerable  value  for 
food,  the  lobster  fisheries  in  particular 
being  of  importance.  The  lobster  is 
highly  esteemed  as  food,  and  is  rapidly 
disappearing  from  our  coasts  as  the 
result  of  overfishing.  Between  twenty 
and  thirty  million  are  yearly  taken  on 
the  North  Atlantic  coast.  This  means 
a  value  at  present  prices  of  about 
5,000,000.  Laws  have  been  enacted  in  New  York  and  other 
states  against  overfishing.  Egg-carrjdng  lobsters  must  be  returned 
to  the  water ;  all  smaller  than  six  to  nine  inches  in  length  (the  law 
varies  in  different  states)  must  be  put  back ;  other  restrictions  are 
placed  upon  the  taking  of  the  animals,  in  hope  of  saving  the  race 
from  extinction.  Some  states  now  hatch  and  care  for  the  young 
for  a  period  of  time  ;  the  United  States  Bureau  of  Fisheries  is  also 
doing  much  good  work,  in  the  hope  of  restocking  to  some  extent 
the  now  almost  depleted  waters. 


North  American  lobster.  This 
specimen,  preserved  at  the 
U.  S.  Fish  Commission  at 
Woods  Hole,  was  of  unusual 
size  and  weighed  over  twenty 
pounds. 


THE  ECONOMIC  IMPORTANCE  OF  ANIMALS     199 


%. 

••^■^^   '- 

;^- 

The  edible  blue  crab.  (From  a  photograph 
loaned  by  the  American  Museum  of 
Natural  History.) 


Several  other  common  crustaceans  are  near  relatives  of  the  crayfish. 
Among  them  are  the  shrimp  and  prawn,  thin-shelled,  active  crustaceans 
common  along  our  eastern  coast.  In  spite  of  the  fact  that  they  form  a 
large  part  of  the  food  supply  of  many  marine  animals,  especially  fish, 
they  do  not  appear  to  be  decreasing  in  numbers.  They  are  also  used 
as  food  by  man,  the  shrimp  fish- 
eries in  this  country  aggregating 
over  $1,000,000  yearly. 

Another  edible  crustacean  of 
considerable  economic  impor- 
tance is  the  blue  crab.  Crabs 
are  found  inhabiting  muddy  bot- 
toms ;  in  such  localities  they  are 
caught  in  great  numbers  in  nets 
or  traps  baited  with  decaying 
meat.  They  are,  indeed,  among 
our  most  valuable  sea  scavengers, 
although  they  are  carnivorous 
hunters  as  well.  The  young  crabs  differ  considerably  in  form  from  the 
adult.  They  undergo  a  complete  metamorphosis  (change  of  form). 
Immediately  after  molting  or  shedding  of  the  outer  shell  in  order  to  grow 
larger,  crabs  are  greatly  desired  by  man  as  an  article  of  food.  They  are 
then  known  as  "  shedders,"  or  soft-shelled  crabs. 

MoUusks  as  Food.  —  Oysters  are  never  found  in  muddy  localities,  for  in 
such  places  they  would  be  quickly  smothered  by  the  sediment  in  the 
water.  They  are  found  in  nature  clinging  to  stones  or  on  shells  or  other 
objects  which  project  a  little  above  the  bottom.     Here  food  is  abundant 

and  oxygen  is  obtained  from  the  water  sur- 
rounding them.  Hence  oyster  raisers  throw 
oyster  shells  into  the  water  and  the  young 
oysters  attach  themselves. 

In  some  parts  of  Europe  and  this  country 
where  oysters  are  raised  artificially,  stakes 
or  brush  are  sunk  in  shallow  water  so  that 
the  young  oyster,  which  is  at  first  free- 
swimming,  may  escape  the  danger  of  smothering  on  the  bottom.  After 
the  oysters  are  a  year  or  two  old,  they  are  taken  up  and  put  down  in 
deeper  water  as  seed  oysters.  At  the  age  of  three  and  four  years  they 
are  ready  for  the  market. 
The  oyster  industry  is  one  of  the  most  profitable  of  our  fisheries.     Nearly 


The  oyster. 


200    THE   ECONOMIC   IMPORTANCE  OF  ANIMALS 


$15,000,000  a  year  has  been  derived  during  the  last  decade  from  such 
sources.  Hundreds  of  boats  and  thousands  of  men  are  engaged  in  dredg- 
ing for  oysters.  Three  of  the  most  important  of  our  oyster  grounds  are 
Long  Island  Sound,  Narragansett  Bay,  and  Chesapeake  Bay. 

Sometimes  oysters  are  artificially  "  fattened  "  by  placing  them  on  beds 
near  the  mouths  of  fresh-water  streams.     Too  often  these  streams  are  the 

bearers  of  much  sewage? 
and  the  oyster,  which  lives 
on  microscopic  organisms, 
takes  in  a  number  of  bac- 
teria with  other  food. 
Thus  a  person  might  be- 
come infected  with  the 
typhoid  bacillus  by  eating 
raw  oj^sters.  State  and 
city  supervision  of  the 
oyster  industry  makes  this 
possibility  very  much  less 
than  it  was  a  few  years 
ago,  as  careful  bacterio- 
logical analysis  of  the 
surrounding  water  is  con- 
stantly made  by  com- 
petent experts. 

Clams.  —  Other  bivalve 
moUusks  used  for  food  are 
clams  and  scallops.  Two 
species  of  the  former  are 
known  to  New  Yorkers, 
one  as  the  "  round,"  an- 
other as  the  "  long  "  or 
''soft-sheUed"  clams.  The 
former  ( Venus  mercenaria) 
was  called  by  the  Indians 
"  quahog,"  and  is  still  so 
called  in  the  Eastern  states.  The  blue  area  of  its  shell  was  used  by  the 
Indians  to  make  wampum,  or  money.  The  quahog  is  now  extensively 
used  as  food.  The  "  long  "  clam  {My a  arenaria)  is  considered  better 
eating  by  the  inhabitants  of  Massachusetts  and  Rhode  Island.  This 
clam  was  highly  prized  as  food  by  the  Indians.    The  clam  industries  of 


This  diagram  shows  how  cases  of  intestinal  disease 
(typhoid  and  diarrhea)  have  been  traced  to 
oysters  from  a  locality  where  they  were  "  fat- 
tened "  in  water  contaminated  with  sewage. 
(Loaned  by  American  Museum  of  Natural 
History.) 


THE   ECONOMIC   IMPORTANCE  OF   ANIMALS    201 

the  eastern  coast  aggregate  nearly  $1,000,000  a  year.  The  dredging  for 
scallops,  another  molluscan  delicacy,  forms  an  important  industry  along 
certain  parts  of  the  eastern  coast. 

Fish  as  Food.  —  Fish  are  used  as  food  the  world  over.  From 
very  early  times  the  herring  were  pursued  by  the  Norsemen. 
Fresh-water  fish,  such  as 
whitefish,  perch,  pickerel, 
pike,  and  the  various  mem- 
bers of  the  trout  family,  are 
esteemed  food  and,  espe- 
cially in  the  Great  I^ake 
region,  form  important  fish- 
eries. But  by  far  the  most 
important  food  fishes  are 
those  which  ^re  taken  in 
salt  water.  Here  we  have 
two  types  of  fisheries,  those 

where  the  fish  comes  up  Salmon  leaping  a  fall  on  their  way  to  their 
a    river     to     spawn,    as    the         spawning    beds.       (Photographed    by    Dr. 

John  A.  Sampson.) 

salmon,  sturgeon,  or  shad, 

and  those  in  which  fishes  are  taken  on  their  feeding  grounds  in 
the  open  ocean.  Herring  are  the  world's  most  important  catch, 
though  not  in  this  country.     Here  the   salmon  of  the  western 


m*- 


^ 


"S2S 


Globe  P'isheries. 


202     THE   ECONOMIC   IMPORTANCE  OF   ANIMALS 

coast  is  taken  to  the  value  of  over  $13,000,000  a  year.  Cod 
fishing  also  forms  an  important  industry;  over  7000  men  being 
employed  and  over  $2,000,000  of  codfish  being  taken  each  year 
in  this  country. 

Hundreds  of  other  species  of  fish  are  used  as  food,  the  fish  that 
is  nearest  at  hand  being  often  the  cheapest  and  best.  Why, 
for  example,  is  the  flounder  so  cheap  in  the  New  York  markets? 
In  what  waters  are  the  cod  and  herring  fisheries,  sardine,  oyster, 
sponge,  pearl  oyster?     (See  chart  on  page  201.) 

Amphibia  and  Reptiles  as  Food.  —  Frogs'  legs  are  esteemed  a 
delicacy.  Certain  reptiles  are  used  as  food  by  people  of  other 
nationalities,  the  Iguana,  a  Mexican  lizard,  being  an  example. 
Many  of  the  sea-Avater  turtles  are  of  large  size,  the  leatherback  and 
the  green  turtle  often  weighing  six  hundred  to  seven  hundred 
pounds  each.  The  flesh  of  the  green  turtle  and  especially  of  the 
diamond-back  terrapin,  an  animal  found  in  the  salt  marshes  along 
our  southeastern  coast,  is  highly  esteemed  as  food.  Unfortunately 
for  the  preservation  of  the  species,  these  animals  are  usually  taken 
during  the  breeding  season  when  they  go  to  sandy  beaches  to  lay 
their  eggs. 

Birds  as  Food.  —  Birds,  both  wild  and  domesticated,  form  part 
of  our  food  supply.  Unfortunately  our  wild  game  birds  are  dis- 
appearing so  fast  that  we  should  not  consider  them  as  a  source 
of  food.  Our  domestic  fowls,  turkey,  ducks,  etc.,  form  an  impor- 
tant food  supply  and  poultry  farms  give  lucrative  employment 
to  many  people.  Eggs  of  domesticated  birds  are  of  great  impor- 
tance as  food,  and  egg  albumin  is  used  for  other  purposes,  — 
clarifying  sugars,  coating  photographic  papers,  etc. 

Mammals  as  Food.  —  When  we  consider  the  amount  of  wealth 
invested  in  cattle  and  other  domesticated  animals  bred  and  used 
for  food  in  the  United  States,  we  see  the  great  economic  impor- 
tance of  mammals.  The  United  States,  Argentina,  and  Australia 
are  the  greatest  producers  of  cattle.  In  this  country  hogs  are 
largely  raised  for  food.  They  are  used  fresh,  salted,  smoked  as 
ham  and  bacon,  and  pickled.  Sheep,  which  are  raised  in  great 
quantities  in  Australia,  Argentina,  Russia,  Uruguay,  and  this 
country,  are  one  of  the  world's  greatest  meat  supplies. 


THE  ECONOMIC  IMPORTANCE  OF  ANIMALS     203 


Goats,  deer,  many  larger  game  animals,  seals,  walruses,  etc., 
give  food  to  people  who  live  in  parts  of  the  earth  that  are  less 
densely  populated. 

Domesticated  Animals.  —  When  man  emerged  from  his  savage 
state  on  the  earth,  one  of  the  first  signs  of  the  beginning  of  civili- 
zation was  the  domestication 
of  animals.  The  dog,  the  cow, 
sheep,  and  especially  the  horse, 
mark  epochs  in  the  advance  of 
civilization.  Beasts  of  burden 
are  used  the  world  over,  horses 
almost  all  over  the  world,  cer- 
tain cattle,  as  the  water  buffalo, 
in  tropical  Malaysia;  camels, 
goats,  and  the  llama  are  also 
used  as  draft  animals  in  some 
other  countries. 

Man's  wealth  in  many  parts 
of  the  world  is  estimated  in 
terms  of  his  cattle  or  herds  of 
sheep.  So  many  products  come 
from  these  sources  that  a  long 
list  might  be  given,  such  as 
meats,    milk,    butter,    cheese. 


wool,  or  other  body  coverings,  Feeding  silkworms.  The  -caterpillars  are 
1       , -1  1  .  J    1  •  1  1  the  white  objects  in  the  trays. 

leather,  skms,  and  hides   used 

for  other  purposes.  Great  industries  are  directly  dependent  upon 
our  domesticated  animals,  as  the  making  of  shoes,  the  manu- 
facture of  woolen  cloth,  the  tanning  industry,  and  many  others. 

Uses  for  Clothing.  —  The  manufacture  of  silk  is  due  to  the  pro- 
duction of  raw  silk  by  the  silkworm,  the  caterpillar  of  a  moth. 
It  lives  upon  the  mulberry  and  makes  a  cocoon  from  which  the  silk 
is  wound.  The  Chinese  silkworm  is  now  raised  to  a  slight  extent 
in  southern  California.  China,  Japan,  Italy,  and  France,  because 
of  cheaper  labor,  are  the  most  successful  silk-raising  countries. 

The  use  of  wool  gives  rise  to  many  great  industries.  After  the 
wool  is  cut  from  the  sheep,  it  has  to  be  washed  and  scoured  to 


204    THE  ECONOMIC   IMPORTANCE  OF  ANIMALS 


get  out  the  dirt  and  grease.  This  wool  fat  or  lanoline  is  used  in 
making  soap  and  ointments.  The  wool  is  next  "  carded,"  the 
fibers  being  interwoven  by  the  fine  teeth  of  the  carding  machine 
or  "  combed/'  the  fibers  here  being  pulled  out  parallel  to  each 
other.  Carded  wool  becomes  woolen  goods;  combed  wool, 
worsted  goods.     The  wastes  are  also  utilized,  being  mixed  with 

"  shoddy  "  (wool  from 
cloth  cuttings  or  rags) 
to  make  woolen  goods 
of  a  cheap  grade. 

Goat  hair,  especially 
that  of  the  Angora  and 
the  Cashmere  goat,  has 
much  use  in  the  cloth- 
ing industries.  Camel's 
liair  and  alpaca  are 
also  used. 

Fur.  —  The  furs  of 
many  domesticated  and 
wild  animals  are  of  im- 
portance. The  Carniv- 
ora  as  a  group  are  of 
much  economic  importance  as  the  source  of  most  of  our  fur.  The 
fur  seal  fisheries  alone  amount  to  many  millions  of  dollars  annu- 
ally. Otters,  skunks,  sables,  weasels,  foxes,  and  minks  are  of 
considerable  importance  as  fur  producers.  Even  cats  are  now 
used  for  fur,  usually  masquerading  under  some  other  name.  The 
fur  of  the  beaver,  one  of  the  largest  of  the  rodents  or  gnawing 
mammals,  is  of  considerable  value,  as  are  the  coats  of  the 
chinchilla,  muskrats,  squirrels,  and  other  rodents.  The  fur  of  the 
rabbit  and  nutria  are  used  in  the  manufacture  of  felt  hats.  The 
quills  of  the  porcupines  (greatly  developed  and  stiffened  hairs) 
have  a  slight  commercial  value. 

Conservation  of  Fur-bearing  Animals  Needed.  —  As  time  goes 
on  and  the  furs  of  wild  animals  become  scarcer  and  scarcer  through 
overkilling,  we  find  the  need  for  protection  and  conservation  of 
many  of  these  fast-vanishing  wild  forms  more  and  more  impera- 


Polar  bear,  a  fur-bearing  mammal  which  is  rapidly 
being  exterminated.     "Why? 


THE   ECONOMIC   IMPORTANCE   OF  ANIMALS     205 

tive.  Already  breeding  of  some  fur-bearing  animals  has  been 
tried  with  success,  and  cheap  substitutes  for  wild  animal  skins  are 
coming  more  and  more  into  the  markets.  Black-fox  breeding  has 
been  tried  successfully  in  Prince  Edward  Island,  Canada,  S2500 
to  $3000  being  given  for  a  single  skin.  Skunk,  marten,  and  mink 
are  also  being  bred  for  the  market.  Game  preserves  in  this 
country  and  Canada  are  also  helping  to  preserve  our  wild  fur- 
bearing  animals. 

Animal  Oils.  —  Whale  oil,  obtained  from  the  fat  or  "  blubber  " 
of  whales,  is  used  extensively  for  lubricating.  Neat's-foot  oil 
comes  from  the  feet  of  cattle  and  is  also  used  in  lubrication. 
Tallow  and  lard,  two  fats  from  cattle,  sheep,  and  pigs,  have 
so  many  well-known  uses  that  comment  is  unnecessary.  Cod- 
liver  oil  is  used  medically  and  is  well  known.  But  it  is  not 
so  widely  known  that  a  fish  called  the  menhaden  or  "  moss 
bunkers "  of  the  Atlantic  coast  produces  over  3,000,000  gal- 
lons of  oil  every  year  and  is  being  rapidly  exterminated  in 
consequence. 

Hides,  Horns,  Hoofs,  etc.  —  Leathers,  from  cattle,  horses, 
sheep,  and  goats,  are  used  everywhere.  Leather  manufacture  is 
one  of  the  great  industries  of  the  Eastern  states,  hundreds  of 
millions  of  dollars  being  invested  in  its  manufacturing  plants. 
Horns  and  bones  are  utilized  for  making  combs,  buttons,  handles 
for  brushes,  etc.  Glue  is  made  from  the  animal  matter  in  bones. 
Ivory,  obtained  from  elephant,  walrus,  and  other  tusks,  forms  a 
valuable  commercial  product.  It  is  largely  used  for  knife 
handles,  piano  keys,  combs,  etc. 

Perfumes.  —  The  musk  deer,  musk  ox,  and  muskrat  furnish  a 
valuable  perfume  called  musk.  Civet  cats  also  give  us  a  somewhat 
similar  perfume.  Ambergris,  a  basis  for  delicate  perfumes,  comes 
from  the  intestines  of  the  sperm  whale. 

Protozoa.  —  The  Protozoa  have  played  an  important  part  in  rock 
building.  The  chalk  beds  of  Kansas  and  other  chalk  formations  are 
made  up  to  a  large  extent  of  the  tiny  skeletons  of  Protozoa^  called 
Foraminifera.  Some  limestone  rocks  are  also  composed  in  large  part,  of 
such  skeletons.  The  skeletons  of  some  species  are  used  to  make  a  polish- 
ing powder. 


206    THE   ECONOMIC   IMPORTANCE  OF  ANIMALS 


Sponges.  —  The  sponges  of  commerce  have  the  skeleton  composed  of 
tough  fibers  of  material  somewhat  like  that  of  cow's  horn.  This  fiber  is 
elastic  and  has  the  power  of  absorbing  water.  In  a  hving  state,  the 
horny  fiber  sponge  is  a  dark-colored  fleshy  mass,  usually  found  attached  to 
rocks.  The  warm  waters  of  the  Mediterranean  Sea  and  the  West  Indies 
furnish  most  of  our  sponges.  The  sponges  are  pulled  up  from  their  resting 
place  on  the  bottom,  by  means  of  long-handled  rakes  operated  by  men  in 
boats  or  are  secured  by  divers.  They  are  then  spread  out  on  the  shore  in 
the  sun,  and  the  hving  tissues  allowed  to  decay;  then  after  treatment 
consisting  of  beating,  bleaching,  and  trimming,  the  bath  sponge  is  ready 

for  the  market.  Some 
forms  of  coral  are  of  com- 
mercial value.  The  red 
coral  of  the  Mediter- 
ranean Sea  is  the  best 
example. 

Pearls  and  Mother  of 
Pearl.  —  Pearls  are  prized 
the  world  over.  It  is  a 
well-known  fact  that  even 
in  this  country  pearls  of 
some  value  are  sometimes 
found  within  the  shells  of 
the  fresh-water  mussel 
and  the  oyster.  Most  of 
the  finest,  however,  come 
from  the  waters  around 
Ceylon.  If  a  pearl  is  cut  open  and  examined  carefuUy,  it  is  found  to  be 
a  deposit  of  the  mother-of-pearl  layer  of  the  shell  around  some  central 
structure.  It  has  been  beUeved  that  any  foreign  substance,  as  a  grain 
of  sand,  might  irritate  the  mantle  at  a  given  point,  thus  stimulating  it 
to  secrete  around  the  substance.  It  now  seems  likely  that  most  perfect 
pearls  are  due  to  the  growth  within  the  mantle  of  the  clam  or  oyster 
of  certain  parasites,  stages  in  the  development  of  a  flukeworm.  The 
irritation  thus  set  up  in  the  tissue  causes  mother  of  pearl  to  be  deposited 
around  the  source  of  irritation,  with  the  subsequent  formation  of  a  pearl. 
The  pearl-button  industry  in  this  country  is  largely  dependent  upon  the 
fresh-water  mussel,  the  shells  of  which  are  used.  This  mussel  is  being  so 
rapidly  depleted  that  the  national  government  is  working  out  a  means  of 
artificial  propagation  of  these  animals. 


In  some  countries  little  metal  images  of  Buddha  are 
placed  within  the  shells  of  living  pearl  oysters  or 
clams.  Over  these  the  mantle  of  the  animal 
secretes  a  layer  of  mother  of  pearl  as  is  shown  in 
the  picture. 


THE   ECONOMIC   IMPORTANCE  OF   ANIMALS    207 


Honey  and  Wax.  —  Honeybees  ^  are  kept  in  hives.  A  colony 
consists  of  a  queen,  a  female  who  lays  the  eggs  for  the  colony,  the 
drones,  whose  duty  it 
is  to  fertilize  the  eggs, 
and  the  workers. 

The  cells  of  the  comb 
are  built  by  the  workers 
out  of  wax  secreted 
from  the  under  surface 
of  their  bodies.  The 
wax  is  cut  off  in  thin 
plates  by  means  of  the 
wax  shears  between 
the  two  last  joints  of 
the  hind  legs.  These 
cells  are  used  to  place 
the  eggs  of  the  queen 
in,  one  egg  to  each 
cell,  and  the  young  are 
hatched  after  three 
days,  to  begin  life  as 
footless  white  grubs. 

The  young  are  fed 
for  several  days,  then 
shut  up  in  the  cells 
and  allowed  to  form  pupae.  Eventually  they  break  their  cells  and 
take  their  place  as  workers  in  the  hive,  first  as  nurses  for  the 
young  and  later  as  pollen  gatherers  and  honey  makers. 

We  have  already  seen  (pages  37  to  39)  that  the  honeybee 
gathers  nectar,  which  she  swallows,  keeping  the  fluid  in  her  crop 
until  her  return  to  the  hive.     Here  it  is  forced  out  into  cells  of 

1  Their  daily  life  may  be  easily  watched  in  the  schoolroom,  by  means  of  one  of  the 
many  good  and  cheap  observation  hives  now  made  to  be  placed  in  a  window  frame. 
Directions  for  making  a  small  observation  hive  for  school  work  can  be  found  in 
Hodge,  Nature  Study  and  Life,  Chap.  XIV.  Bulletin  No.  1,  U.S.  Department  of 
Agriculture,  entitled  The  Honey  Bee,  by  Frank  Benton,  is  valuable  for  the  amateur 
beekeeper.  It  may  be  obtained  for  twenty-five  cents  from  the  Superintendent  of 
Documents,  Union  Building,  Washington,  D.C. 


Cells  of  honeycomb,  queen  cell  on  right  at  bottom. 


208    THE  ECONOMIC   IMPORTANCE   OF  ANIMALS 


the  comb.  It  is  now  thinner  than  what  we  call  honey.  To  thicken 
it,  the  bees  swarm  over  the  open  cells,  moving  their  wings  very 
rapidly,  thus  evaporating  some  of  the  water.  A  hive  of  bees 
have  been  known  to  make  over  thirty-one  pounds  of  honey  in  a 
single  day,  although  the  average  is  very  much  less  than  this.  It 
is  estimated  from  twenty  to  thirty  millions  of  dollars'  worth  of 
honey  and  wax  are  produced  each  year  in  this  country. 

Cochineal  and  Lac.  —  Among  other  products  of  insect  origin 
is  cochineal,  a  red  coloring  matter,  which  consists  of  the  dried 
bodies  of  a  tiny  insect,  one  of  the  plant  lice  which  lives  on  the 
cactus  plants  in  Mexico  and  Central  America.  The  lac  insect, 
another  one  of  the  plant  lice,  feeds  on  the  juices  of  certain  trees 
in  India  and  pours  out  a  substance  from  its  body  which  after 

treatment  forms  shellac.  Shel- 
lac is  of  much  use  as  a  basis 
for  varnish. 

Gall  Insects.  —  Oak  galls, 
growths  caused  by  the  sting  of 
wasp-like  insects,  give  us  prod- 
ucts used  in  ink  making,  in  tan- 
ning, and  in  making  pjTogaliic 
acid  which  is  much  used  in 
developing  photographs. 

Insects  destroy  Harmful 
Plants  or  Animals.  —  Some 
forms  of  animal  life  are  of  great 
importance  because  of  their  de- 
struction of  harmful  plants  or 
animals. 

A  near  relative  of  the  bee, 
called  the  ichneumon  fly,  does  man  indirectly  considerable  good 
because  of  its  habit  of  laying  its  eggs  and  rearing  the  young  in 
the  bodies  of  caterpillars  which  are  harmful  to  vegetation.  Some 
of  the  ichneumons  even  bore  into  trees  in  order  to  deposit  their 
eggs  in  the  larvae  of  wood-boring  insects.  It  is  safe  to  say  that 
the  ichneumons  save  millions  of  dollars  yearly  to  this  country. 
Several  beetles  are  of  value  to  man.     Most  important  of  these 


An  insect  friend  of  man.  An  ichneumon 
fly  boring  in  a  tree  to  lay  its  eggs  in 
the  burrow  of  a  boring  insect  harmful 
to  that  tree. 


THE  ECONOMIC   IMPORTANCE  OF  ANIMALS     209 


is  the  natural  enemy  of  the  orange-tree  scale,  the  ladybug,  or 
ladybird  beetle.  In  New  York  state  it  may  often  be  found  feed- 
ing upon  the  plant  lice,  or  aphids,  which  Uve  on  rosebushes.  The 
carrion  beetles  and  many  water  beetles  act  as  scavengers.  The 
sexton  beetles  bury  dead  carcasses  of  animals.  Ants  in  tropical 
countries  are  particularly  useful  as  scavengers. 

Insects,  besides  pollinating  flowers,  often  do  a  service  by  eating 
harmful  weeds.  Thus  many  harmful  plants  are  kept  in  check. 
We  have  noted  that  they  spin  silk,  thus  forming  clothing ;  that 
in  many  cases  they  are  preyed  upon,  and  that  they  supply  an 
enormous  multitude  of  birds,  fishes,  and  other  animals  with  food. 

Use  of  the  Toad.  —  The  toad  is  of  great  economic  importance 
to  man  because  of  its  diet.  No  less  than  eighty-three  species  of 
insects,  mostly  injuri- 
ous, have  been  proved 
to  enter  into  the  dietarv. 
A  toad  has  been  ob- 
served to  snap  up  one 
hundred  and  twenty- 
eight  flies  in  half  an 
hour.  Thus  at  a  low 
estimate  it  could  easily 
destroy  one  hundred 
insects  during  a  day 
and  do  an  immense  ser- 
vice to  the  garden  dur- 
ing the  summer.  It  has 
been  estimated  bv  Kirk- 

land  that  a  single  toad  may,  on  account  of  the  cutworms  which 
it  kills,  be  worth  $19.88  each  season  it  lives,  if  the  damage  done 
by  each  cutworm  be  estimated  at  only  one  cent.  Toads  also 
feed  upon  slugs  and  other  garden  pests. 

Birds  eat  Insects.  —  The  food  of  birds  makes  them  of  the 
greatest  economic  importance  to  our  country.  This  is  because 
of  the  relation  of  insects  to  agriculture.  A  large  part  of  the  diet 
of  most  of  our  native  birds  includes  insects  harmful  to  vegetation. 
Investigations  undertaken  by  the  United  States  Department  of 


The  common  toad,  an  insect  cater. 


HUNTER,    CIV.    BI. 


14 


210    THE   ECONOMIC   IMPORTANCE   OF   ANIMALS 

Agriculture  (Division  of  Biological  Survey)  show  that  a  surpris- 
ingly large  number  of  birds  once  believed  to  harm  crops  really 
perform  a  service  by  killing  injurious  insects.  Even  the  much 
maligned  crow  lives  to  some  extent  upon  insects.  Swallows  in  the 
Southern  states  kill  the  cotton-boll  weevil,  one  of  our  worst  insect 

pests.  Our  earliest  visitor,  the 
bluebird,  subsists  largely  on  injuri- 
ous insects,  as  do  woodpeckers, 
cuckoos,  kingbirds,  and  many 
others.  The  robin,  whose  pres- 
ence in  the  cherry  tree  we  resent, 
during  the  rest  of  the  summer 
does  much  good  by  feeding  upon 
noxious  insects.  Birds  use  the 
food  substances  which  are  most 
abundant  around  them  at  the 
time.^ 

Birds  eat  Weed  Seeds.  —  Not 
only  do  birds  aid  man  in  his 
battles  with  destructive  insects, 
but  seed-eating  birds  eat  the  seeds 
of  weeds.  Our  native  sparrows 
(not    the    English    sparrow),    the 

Food  of  some  common  birds.    Which   Hiourning    dove,    bobwhite,    and 
of  the  above  birds  should  be  pro-   other  birds  feed  largely  upon  the 

tected  by  man  and  why  ?  i         r  r 

seeds  oi  many  oi  our  common 
weeds.  This  fact  alone  is  sufficient  to  make  birds  of  vast  eco- 
nomic importance. 


AMERICAN  CROW 


ENGLISH  SPARROW 


'  The  following  quotation  from  I.  P.  Trimble,  A  Treatise  on  the  Insect  Enemies  of 
Fruit  and  Shade  Trees,  bears  out  this  statement :  "On  the  fifth  of  May,  1864,  .  .  - 
seven  different  birds  ,  .  .  had  been  feeding  freely  upon  small  beetles.  .  .  .  There 
was  a  great  flight  of  beetles  that  day;  the  atmosphere  was  teeming  with  them. 
A  few  days  after,  the  air  was  filled  with  Ephemera  flies,  and  the  same  species  of  birds 
were  then  feeding  upon  them." 

During  the  outbreak  of  Rocky  Mountain  locusts  in  Nebraska  in  1874-1877, 
Professor  Samuel  Aughey  saw  a  long-billed  marsh  wren  carry  thirty  locusts  to  her 
young  in  an  hour.  At  this  rate,  for  sevei  hours  a  day,  a  brood  would  consume  210 
locusts  per  day,  and  the  passerine  birds  of  the  eastern  half  of  Nebraska,  allowing 
only  twenty  broods  to  the  square  mile,  would  destroy  daily  162,771,000  of  the 


THE   ECONOMIC   IMPORTANCE  OF   ANIMALS     211 

Not  all  birds  are  seed  or  insect  feeders.  Some,  as  the  cormorants, 
ospreys,  gulls,  and  terns,  are  active  fishers.  Near  large  cities 
gulls  especially  act  as  scavengers,  destroying  much  floating  gar- 
bage that  otherwise  might  be  washed  ashore  to  become  a  menace 
to  health.  The  vultures  of  India  and  semitropical  countries  are 
of  immense  value  as  scavengers.  Birds  of  prey  (owls)  eat  living 
mammals,  including  many  rodents ;  for  example,  field  mice,  rats, 
and  other  pests. 

Extermination  of  our  Native  Birds.  —  Within  our  own  times 
we  have  witnessed  the  almost  total  extermination  of  some  species 
of  our  native  birds.  The  American  passenger  pigeon,  once  very 
abundant  in  the  Middle  West,  is  now  extinct.  Audubon,  the 
greatest  of  all  American  bird  lovers,  gives  a  graphic  account  of 
the  migration  of  a  flock  of  these  birds.  So  numerous  were  they 
that  when  the  flock  rose  in  the  air  the  sun  was  darkened,  and 
at  night  the  weight  of  the  roosting  birds  broke  down  large  branches 
of  the  trees  in  which  they  rested.  To-day  not  a  single  wild  speci- 
men of  this  pigeon  can  be  found,  because  they  were  slaughtered 
by  the  hundreds  of  thousands  during  the  breeding  season. 
The  wholesale  killing  of  the  snowy  egret  to  furnish  ornaments 
for  ladies'  headwear  is  another  example  of  the  improvidence 
of  our  fellow-countrymen.  Charles  Dudley  Warner  said, ''  Feathers 
do  not  improve  the  appearance  of  an  ugly  woman,  and  a  pretty 
woman  needs  no  such  aid."  Wholesale  killing  for  plumage,  eggs, 
and  food,  and,  alas,  often  for  mere  sport,  has  reduced  the  numl:)er 
of  our  birds  more  than  one  half  in  thirty  states  and  territories  within 
the  past  fifteen  years.  Every  crusade  against  indiscriminate 
killing  of  our  native  birds  should  be  welcomed  by  all  thinking 

pests.  The  average  locust  weighs  about  fifteen  grains,  and  is  capable  each  day  of 
consuming  its  own  weight  of  standing  forage  crops,  which  at  SIO  per  ton  would  be 
worth  $1743.26.  This  case  may  serve  as  an  illustration  of  the  vast  good  that  is 
done  every  year  by  the  destruction  of  insect  pests  fed  to  nestling  birds.  And  it 
should  be  remembered  that  the  nesting  season  is  also  that  when  the  destruction  of 
injurious  insects  is  most  needed ;  that  is,  at  the  period  of  greatest  agricultural 
activity  and  before  the  parasitic  insects  can  be  depended  on  to  reduce  the  pests. 
The  encouragement  of  birds  to  nest  on  the  farm  and  the  discouragement  of  nest 
robbing  are  therefore  more  than  mere  matters  of  sentiment ;  they  return  an  actual 
cash  equivalent,  and  have  a  definite  bearing  on  the  success  or  failure  of  the  crops.  — 
Year  Book  of  the  Department  of  Agriculture. 


212    THE  ECONOMIC   IMPORTANCE   OF  ANIMALS  . 

Americans.  The  recent  McLane  bill  which  aims  at  the  protec- 
tion of  migrating  birds  and  the  bird-protecting  clause  of  the 
recently  passed  tariff  bill  shows  that  this  country  is  awaking  to 
the  value  of  her  bird  life.  Without  the  birds  the  farmer  would 
have  a  hopeless  fight  against  insect  pests.  The  effect  of  killing 
native  birds  is  now  well  seen  in  Italy  and  Japan,  where  insects  are 
increasing  and  do  greater  damage  each  year  to  crops  and  trees. 

Of  the  eight  hundred  or  more  species  of  birds  in  the  United 
States,  only  six  species  of  hawks  (Cooper's  and  the  sharp-shinned 
hawk  in  particular),  and  the  great  horned  owl,  which  prey  upon 
useful  birds ;  the  sapsucker,  which  kills  or  injures  many  trees  be- 
cause of  its  fondness  for  the  growing  layer  of  the  tree  ;  the  bobolink^ 
which  destroys  yearly  $2,000,000  worth  of  rice  in  the  South ;  the 
crow,  which  feeds  on  crops  as  well  as  insects;  and  the  English 
sparrow,  may  be  considered  as  enemies  of  man. 

The  English  Sparrow.  —  The  English  sparrow  is  an  example  of 
a  bird  introduced  for  the  purpose  of  insect  destruction,  that  has 
done  great  harm  because  of  its  relation  to  our  native  birds.  In- 
troduced at  Brooklyn  in  1850  for  the  purpose  of  exterminating 
the  cankerworm,  it  soon  abandoned  an  insect  diet  and  has  driven 
out  most  of  our  native  insect  feeders.  Investigations  by  the 
United  States  Department  of  Agriculture  have  shown  that  in 
the  country  these  birds  and  their  young  feed  to  a  large  extent 
upon  grain,  thus  showing  them  to  be  injurious  to  agriculture. 
Dirty  and  very  prolific,  it  already  has  worked  its  way  from  the 
East  as  far  as  the  Pacific  coast.  In  this  area  the  bluebird,  song 
sparrow,  and  yellowbird  have  all  been  forced  to  give  way,  as  well 
as  many  larger  birds  of  great  economic  value  and  beauty.  The 
English  sparrow  has  become  a  pest  especially  in  our  cities,  and 
should  be  exterminated  in  order  to  save  our  native  birds.  It  is 
feared  in  some  quarters  that  the  English  starling  which  has  re- 
cently been  introduced  into  this  country  may  in  time  prove  a 
pest  as  formidable  as  the  English  sparrow. 

Food  of  Snakes.  —  Probably  the  most  disliked  and  feared  of  all 
animals  are  the  snakes.  This  feeling,  however,  is  rarely  deserved, 
for,  on  the  whole,  our  common  snakes  are  beneficial  to  man.  The 
black  snake  and  the  milk  snake  feed  largely  on  injurious  rodents 


THE  ECONOMIC   IMPORTANCE  OF  ANIMALS    213 


(rats,  mice,  etc.),  the  pretty 
green  snake  eats  injurious  in- 
sects, and  the  Uttle  DeKay 
snake  feeds  partially  on  slugs. 
If  it  were  not  that  the  rattle- 
snake and  the  copperhead  are 
venomous,  they  also  could  be 
said  to  be  useful,  for  they  live 
on  English  sparrows,  rats,  mice, 
moles,  and  rabbits. 

Food  of  Herbivorous  Ani- 
mals. —  We  must  not  forget 
that  other  animals  besides  in- 
sects and  birds  help  to  keep 
down  the  rapidly  growing  weeds. 
Herbivorous  animals  the  world 
over  destroy,  besides  the  grass 
which  they  eat,  untold  multi- 
tudes of  weeds,  which,  if  un- 
checked, would  drive  out  the 
useful  occupants  of  the  pasture, 
the  grasses  and  grains. 

HARM    DONE    BY 
ANIMALS 

Economic  Loss  from  Insects. 
—  The  money  value  of  crops, 
forest  trees,  stored  foods,  and 
other  material  destroyed  annu- 
ally by  insects  is  beyond  belief. 
It  is  estimated  that  they  get 
one  tenth  of  the  country's  crops, 
at  the  lowest  estimate  a  matter 
of  some  $300,000,000  yearly. 
''  The  common  schools  of  the 
country  cost  in  1902  the  sum 
of  $235,000,000,  and  all  higher 


This  shows  how  sonu^  siuikos  (constric- 
tors) kill  and  eat  their  prey.  (Series 
photographed  by  C.  W.  Beebe  and 
Claxence  Halter.) 


214    THE   ECONOMIC   IMPORTANCE  OF  ANIMALS 


institutions  of  learning  cost  less  than  $50,000,000,  making  the 
total  cost  of  education  in  the  United  States  considerably  less  than 
the  farmers  lost  from  insect  ravages. 

''  Furthermore,  the  yearly  losses  from  insect  ravages  aggregate 
nearly  twice  as  much  as  it  costs  to  maintain  our  army  and  navy ; 
more  than  twice  the  loss  by  fire ;  twice  the  capital  invested  in 
manufacturing  agricultural  implements ;  and  nearly  three  times 
the  estimated  value  of  the  products  of  all  the  fruit  orchards,  vine- 
yards, and  small  fruit  farms  in  the  country."  —  Slingerland. 

The  total  3^early  value  of  all  farm  and  forest  products  in  New 
York  is  perhaps  $150,000,000,  and  the  one  tenth  that  the  insects 
get  is  worth  $15,000,000. 

Insects  which  damage  Garden  and  Other  Crops.  —  The  grass- 
hoppers and  the  larviB  of  various  moths  do   considerable   harm 

here,  especially  the  ^'  cab- 
bage worm,"  the  cutworm, 
a  feeder  on  all  kinds  of 
garden  truck,  and  the  corn 
worm,  a  pest  on  corn,  cot- 
ton, tomatoes,  peas,  and 
beans. 

Among  the  beetles  which 
are  found  in  gardens  is 
the  potato  beetle,  which 
destroys  the  potato  plant. 
This  beetle  formerly  lived 
in  Mexico  upon  a  wild 
plant  of  the  same  family 
as  the  potato,  and  came 
north  upon  the  introduc- 
tion   of    the  potato   into 


Cott(Mi-l)oll  weevil,  a,  larva ;  h,  pupa  ;  c,  adult. 
Enlarged  about  four  times.  (Photographed 
by  Davison.) 


Colorado,  evidently  preferring  cultivated  forms  to  wild  forms  of 
this  family. 

• 

The  one  beetle  doing  by  far  the  greatest  harm  in  this  country  is 
the  cotton-boll  weevil.  Imported  from  Mexico,  since  1892  it  has 
spread  over  eastern  Texas  and  into  Louisiana.  The  beetle  lays 
its  eggs  in  the  young  cotton  fruit  or  boll,  and  the  larvae  feed  upon 


THE   ECONOMIC   IMPORTANCE   OF  ANIMALS    215 

the  substance  within  the  boll.  It  is  estimated  that  if  unchecked 
this  pest  would  destroy  yearly  one  half  of  the  cotton  crop, 
causing  a  loss  of  $250,000,000.  Fortunately,  the  United  States 
Department  of  Agriculture  is  at  work  on  the  problem,  and,  while 
it  has  not  found  any  way  of  exterminating  the  beetle  as  yet,  it  has 
been  found  that,  by  planting  more  hardy  varieties  of  cotton,  the 
crop  matures  earlier  and  ripens  before  the  weevils  have  increased 
in  sufficient  numbers  to  destroy  the  crop  (see  page  126). 

The  bugs  are  among  our  most  destructive  insects.  The  most 
familiar  examples  of  our  garden  pests  are  the  squash  bug;  the 
chinch  bug,  which  yearly  does  damage  estimated  at  $20,000,000,  by 
sucking  the  juice  from  the  leaves  of  grain ;  and  the  plant  lice,  or 
aphids.  One,  hving  on  the  grape,  yearly  destroys  immense  num- 
bers of  vines  in  the  vineyards  of  France,  Germany,  and  California. 

Insects  which  harm  Fruit  and  Forest  Trees.  —  Great  damage  is 
annually  done  trees  by  the  larvae  of  moths.     Massachusetts  has 


Female  tussock  moth  which  has 
just  emerged  from  the  cocoon 
at  the  left,  upon  which  it  has 
deposited  over  two  hundred 
eggs.  (Photograph        by 

Davison.) 


Caterpillar    of    tussock    moth, 
graph  by  Davison.) 


(Photo- 


already  spent  over  $3,000,000  in  trying  to  exterminate  the  imported 
gypsy  moth.  The  codling  moth,  which  bores  into  apples  and  pears, 
is  estimated  to  ruin  yearly  $3,000,000  worth  of  fruit  in  New  York 
alone,  which  is  by  no  means  the  most  important  apple  region  of 
the  United  States.  Among  these  pests,  the  most  important  to 
the  dweller  in  a  large  city  is  the  tussock  moth,  which  destroys  our 
shade  trees.     The  caterpillar  may  easily  be  recognized  by  its  hairy, 


216     THE   ECONOMIC   IMPORTANCE   OF  ANIMALS 

tufted  red  head.  The  eggs  are  laid  on  the  bark  of  shade  trees  in 
what  look  like  masses  of  foam.  (See  figure  on  page  215.)  By 
collecting  and  burning  the  egg  masses  in  the  fall,  we  may  save 
many  shade  trees  the  following  year. 

The  larvse  of  some  moths  damage  the  trees  by  boring  into  the 
wood  of  the  tree  on  which  they  live.  Such  are  the  peach,  apple, 
and  other  fruit-tree  borers  common  in  our  orchards.  Many  beetle 
hirvae  also  live  in  trees  and  kill  annually  thousands  of  forest  and 
shade  trees.  The  hickory  borer  threatens  to  kill  all  the  hickory, 
trees  in  the  Eastern  states. 

Among  the  bugs  most  destructive  to  trees  are  the  scale  insect 
and  the  plant  lice.  The  San  Jose  scale,  a  native  of  China,  was 
introduced  into  the  fruit  groves  of  California  about  1870  and  has 
spread  all  over  the  country.  A  ladybird  beetle,  which  has  also  been 
imported,  is  the  most  effective  agent  in  keeping  this  pest  in  check. 

Insects  of  the  House  or  Storehouse.  —  Weevils  are  the  greatest 
pests,  frequently  ruining  tons  of  stored  corn,  wheat,  and  other 
cereals.  Roaches  will  eat  almost  anything,  even  clothing;  they 
are  especially  fond  of  all  kinds  of  breadstuff s.  The  carpet  beetle 
is  a  recognized  foe  of  the  housekeeper,  the  larvse  feeding  upon  all 
sorts  of  woolen  material.  The  larvse  of  the  clothes  moth  do  an 
immense  amount  of  damage,  especially  to  stored  clothing.  Fleas, 
lice,  and  particularly  bedbugs  are  among  man's  personal  foes. 
Besides  being  unpleasant  they  are  believed  to  be  disease  carriers 
and  as  such  should  be  exterminated.^ 

Food  of  Starfish.  —  Starfish  are  enormously  destructive  to  young  clams 
and  oysters,  as  the  following  evidence,  collected  by  Professor  A.  D.  Mead, 
of  Brown  University,  shows.  A  single  starfish  was  confined  in  an  aqua- 
rium with  fifty-six  young  clams.  The  largest  clam  was  about  the  length 
of  one  arm  of  the  starfish,  the  smallest  about  ten  millimeters  in  length. 
In  six  days  every  clam  in  the  aquarium  was  devoured.  Hundreds  of 
thousands  of  dollars'  damage  is  done  annually  to  the  oysters  in  Connecti- 
cut alone  by  the  ravages  of  starfish.  During  the  breeding  season  of  the 
clam  and  oyster  the  boats  dredge  up  tons  of  starfish  which  are  thrown  on 
shore  to  die  or  to  be  used  as  fertihzer. 

'  Directions  for  the  treatment  of  these  pests  may  be  found  in  pamphlets  issued 
by  the  U.  S.  Department  of  Agriculture. 


THE  ECONOMIC  IMPORTANCE  OF  ANIMALS    217 


THE  RELATIONS   OF  ANIMALS   TO   DISEASE 


^L 


The  Cause  of  Malaria.  —  The  study  of  the  life  history  and 
habits  of  the  Protozoa  has  resulted  in  the  finding  of  many  parasitic 
forms,  and  the  consequent  expla- 
nation of  some  kinds  of  disease. 
One  parasitic  protozoan  like  an 
amoeba  is  called  Plasmodium  ma- 
larice.  It  causes  the  disease 
known  as  malaria.  When  a  mos- 
quito (the  anopheles)  sucks  the 
blood  from  a  person  having  mala- 
ria this  parasite  passes  into  the 
stomach  of  the 
mosquito.  Af- 
ter completing 
a  part  of  its  life 
history  within 
the  mosquito's 
body  the  para- 
site establishes 
itself  within  the 
glands  which 
secrete  the  sa- 
liva of  the  mos- 
quito. After 
about  eight 
days,  if  the  in- 
fected mosquito 
bites  a  person, 
some  of  the 
parasites  are 
introduced  into 

the  blood  along  with  the  saliva.  These  parasites  enter  the  cor- 
puscles of  the  blood,  increase  in  size,  and  then  form  spores.  The 
rapid  process  of  spore  formation  results  in  the  breaking  down 
of  the  blood  corpuscles  and  the  release  of  the  spores,  and  the 


■I     t 


The  life  history  of  th3  malarial  parasite.  This  cut  of  the 
malarial  parasite  shows  parts  of  th^  body  of  the  mosquito 
and  of  man.  To  understand  the  liie  history  begin  at  the 
point  where  the  mosquito  injects  the  crescent-shaped 
bodies  into  the  blood  of  man.  Notice  that  after  the  spores 
are  released  from  the  corpuscles  of  man  two  kinds  of  cells 
may  be  formed.  These  are  probably  a  sexual  stage.  Devel- 
opment within  the  body  of  the  mosquito  will  only  take 
place  when  the  parasite  is  taken  into  its  body  at  this 
sexual  stage.  ^ 


218    THE   ECONOMIC   IMPORTANCE   OF  ANIMALS 

poisons  they  manufacture,  into  the  blood.  This  causes  the  chill 
followed  by  the  fever  so  characteristic  of  malaria.  The  spores 
may  again  enter  the  blood  corpuscles  and  in  forty-eight  or 
seventy-two  hours  repeat  the  process  thus  described,  depending 
on  the  kind  of  malaria  they  cause.  The  only  cure  for  the 
disease  is  quinine  in  rather  large  doses.  This  kills  the  parasites 
in  the  blood.  But  quinine  should  not  be  taken  except  under 
a  physician's  directions. 

The  Malarial  Mosquito.  —  Fortunately  for  mankind,  not  all 
mosquitoes  harbor  the  parasite  which  causes  malaria.  The  harm- 
less mosquito  (culex)  may  be  usually  distinguished  from  the 
mosquito  which  carries  malaria  {anopheles)  by  the  position  taken 


How  to  distinguish  the  harmless  mosquito  (culex),  a,  from  the  malarial  mosquito 
(anopheles),  b,  when  at  rest.     Notice  the  position  of  legs  and  body. 

when  at  rest.  Culex  lays  eggs  in  tiny  rafts  of  one  hundred  or  more 
eggs  in  any  standing  water ;  thus  the  eggs  are  distinguished  from 
those  of  anopheles,  which  are  not  in  rafts.  Rain  barrels,  gutters, 
or  old  cans  may  breed  in  a  short  time  enough  mosquitoes  to  stock 
a  neighborhood.  The  larvse  are  known  as  wigglers.  They  breathe 
through  a  tube  in  the  posterior  end  of  the  body,  and  may  be  rec- 
ognized by  their  peculiar  movement  when  on  their  way  to  the  sur- 
face to  breathe.  The  pupa,  distinguished  by  a  large  thoracic 
region,  breathes  through  a  pair  of  tubes  on  the  thorax.  The  fact 
that  both  larvse  and  pupse  take  air  from  the  surface  of  the  water 
makes  it  possible  to  kill  the  mosquito  during  these  stages  by  pour- 
ing oil  on  the  surface  of  the  water  where  they  breed.  The  intro- 
duction of  minnows,  gold  fish,  or   other  small   fish  which   feed 


THE  ECONOMIC  IMPORTANCE  OF  ANIMALS    219 


upon  the  larvae  in  the  water  where  the  mosquitoes  breed  will  do 
much  to  free  a  neighborhood  from  this  pest.  Draining  swamps 
or  low  land  which  holds  water  after  a  rain  is  another  method  of 
extermination.  Some  of  the  mosquito-infested  districts  around 
New  York  City  have  been  almost  freed  from  mosquitoes  by 
draining  the  salt  marshes  where  they  breed.  Long  shallow 
trenches  are  so  built  as  to  tap  and  drain  off  any  standing  water  in 
which  the  eggs  might  be  laid.  In  this  way  the  mosquito  has 
been  almost  exterminated 
along  some  parts  of  our 
New  England  coast. 

Since  the  beginning  of 
historical  times,  malaria 
has  been  prevalent  in 
regions  infested  by  mos- 
quitoes. The  ancient  city 
of  Rome  was  so  greatly 
troubled  by  periodic  out- 
breaks of  malarial  fever 
that  a  goddess  of  fever 
came  to  be  worshiped  in 
order  to  lessen  the  severity 
of  what  the  inhabitants 
believed  to  be  a  divine  visitation.  At  the  present  time  the 
malaria  of  Italy  is  being  successfully  fought  and  conquered  by 
the  draining  of  the  mosquito-breeding  marshes.  By  a  little  care- 
fully directed  oiling  of  water  a  few  boys  may  make  an  almost 
uninhabitable  region  absolutely  safe  to  live  in.  Why  not  try  it 
if  there  are  mosquitoes  in  your  neighborhood  ? 

Yellow  Fever  and  Mosquitoes.  —  Another  disease  carried  by 
mosquitoes  is  yellow  fever.  In  the  year  1878  there  were  125,000 
cases  and  12,000  deaths  in  the  United  States,  mostly  in  Alabama, 
Louisiana,  and  Mississippi.  During  the  French  occupation  of  the 
Panama  Canal  zone  the  work  was  at  a  standstill  part  of  the  time 
because  of  the  ravages  of  yellow  fever.  Before  the  war  with  Spain 
thousands  of  people  were  ill  in  Cuba.  But  to-day  this  is  changed, 
and  yellow  fever  is  under  almost  complete  control,  both  here  and 


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■  fi^  ■z:iiJ9aKmtm 

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Swamps  are  drained  and  all  standing  water 
covered  with  a  film  of  oil  in  order  to  ex- 
terminate mosquitoes.  Why  is  the  oil 
placed  on  the  surface  of  the  water  ? 


220    THE  ECONOMIC   IMPORTANCE  OF  ANIMALS 


in  the  Canal  zone,  where  the  mosquito  (stegomyia)  which  carried] 

yellow  fever  exists. 

This  is  due  to  the 
experiments  during  the 
summer  of  1900  of  a 
Commission  of  United 
States  army  officers, 
headed  by  Dr.  Walter 
Reed.  Of  these  men  one, 
Dr.  Jesse  Lazear,  gave  up 
his  life  to  prove  experi- 
mentally that  yellow  fever 
was  caused  by  mosquitoes. 
He  allowed  himself  to  be 
bitten  by  a  mosquito  that 
was  known  to  have  bitten 
a  yellow  fever  patient, 
contracted  the  disease, 
and  died  a  martyr  to 
science.  Others,  soldiers, 
volunteered  to  further  test 
by  experiment  how  the 
disease  was  spread,  so 
that  in  the  end  Dr.  Reed 
was  able  to  prove  to  the 
world  that  if  mosquitoes 
could  be  prevented  from 
biting  people  who  had 
yellow  fever  the  disease 
could  not  be  spread.  The 
accompanying  illustration 
shows  the  result   of   this 

Notice  the  difference  in  the  number  of  yearly  knowledge  for  the  city  of 
deaths  from  yellow  fever  before  and  after  XTflVflTia  For  vpars  Hfl- 
the  American  occupation  of  Havana.  navana.      i^  or    years    Jia- 

vana  was  considered  one 
of  the  pest  spots  of  the  West  Indies.  Visitors  shunned  this  port 
and  commerce  was  much  affected  by  the  constant  menace  of 


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IHMK   HHkk«.^ 

1896 

1282                       ^^^Hl 

1897 

— 

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1898  m 

1899  m 

1900 

KUiB 

1901 

18 

Carrier  of  Yelloar  Teuer  discoimred 

\90l 

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1903 

NONE 

1 

1904 

NONE 

1905 

1    £4                               Tirst  Cuban  R-ule. 

1906 

1    l£ 

1907 

3 

1908 

3 

1909 

NONE 

1910 

NONE 

THE  ECONOMIC  IMPORTANCE  OF  ANIMALS    221 

yellow  fever.  At  the  time  of  the  American  occupation  after  the 
war  with  Spain,  the  experiments  referred  to  above  were  under- 
taken. The  city  was  cleaned  up,  proper  sanitation  introduced, 
screens  placed  in  most  buildings,  and  the  breeding  places  of  the 
mosquitoes  were  so  nearly  destroyed  that  the  city  was  practically 
free  from  mosquitoes.  The  result,  so  far  as  yellow  fever  was  con- 
cerned, was  startling,  as  you  can  see  by  reference  to  the  chart. 
Notice  also  the  rise  in  the  death  rate  when  the  young  Cuban 
Republic  took  control.  How  do 
you  account  for  that  ?  We  all  know 
what  American  scientific  medicine 
and  sanitation  is  doing  in  Panama 
and  in  the  Philippines. 

Other  Protozoan  Diseases.  — 
Many  other  diseases  of  man  are 
probably  caused  by  parasitic  pro- 
tozoans. Dysentery  of  one  kind 
appears  to  be  caused  by  the  pres- 
ence of  an  amoeba-like  animal  in  the 
digestive  tract  which  comes  usually 

through    an  impure   water   supply.  s^^^T^;.  *(lftrHowid.r"°" 
Smallpox,  rabies,  and  possibly  other 

diseases  are  caused  by  protozoans.  Smallpox,  which  was  once  the 
most  dreaded  disease  known  to  man,  because  of  its  spread  in 
epidemics,  has  been  conquered  by  vaccination,  of  which  we  shall 
learn  more  later.  The  death  rate  from  rabies  or  hydrophobia  has 
in  a  like  manner  been  greatly  reduced  by  a  treatment  founded  on 
the  same  principles  as  vaccination  and  invented  by  Louis  Pasteur. 
Another  group  of  protozoan  parasites  are  called  trypanosomes. 
These  are  parasitic  in  insects,  fish,  reptiles,  birds,  and  mammals 
in  various  parts  of  the  world.  They  cause  various  diseases  of 
cattle  and  other  domestic  animals,  being  carried  to  the  animal  in 
most  cases  by  flies.  One  of  this  family  is  believed  to  live  in  the 
blood  of  native  African  zebras  and  antelopes ;  seemingly  it  does 
them  no  harm.  But  if  one  of  these  parasites  is  transferred  by  the 
dreaded  tsetse  fly  to  one  of  the  domesticated  horses  or  cattle  of 
the  colonist  of  that  region,  death  of  the  animal  results. 


222    THE   ECONOMIC   IMPORTANCE  OF  ANIMALS 

Another  fly  carries  a  species  of  trypanosome  to  the  natives  of 
Central  Africa,  which  causes  ''  the  dreaded  and  incurable  sleep- 
ing sickness."  This  disease  carries  off  more  than  fifty  thousand 
natives  yearly,  and  many  Europeans  have  succumbed  to  it.  Its 
ravages  are  now  largely  confined  to  an  area  near  the  large  Central 
African  lakes  and  the  Upper  Nile,  for  the  fly  which  carries  the 
disease  lives  near  water,  seldom  going  more  than  150  feet  from 
the  banks  of  streams  or  lakes.  The  British  government  is  now 
trying  to  control  the  disease  in  Uganda  by  moving  all  the  villages 
at  least  two  miles  from  the  lakes  and  rivers.  Among  other 
diseases  that  may  be  due  to  protozoans  is  kala-agar,  a  fever  in  hot 
Asiatic  countries  which  is  probably  carried  by  the  bedbug,  and 
African  tick  fever,  probably  carried  by  a  small  insect  called  the 
tick.  Bubonic  plague,  one  of  the  most  dreaded  of  all  bacterial 
diseases,  is  carried  to  man  by  fleas  from  rats.  In  this  country 
many  fatal  diseases  of  cattle,  as  '^  tick,"  or  Texas  cattle  fever,  are 
probably  caused  by  protozoans. 

The  Fly  a  Disease  Carrier.  —  We  have  already  seen  that  mos- 
quitoes of  different  species  carry  malaria  and  yellow  fever.  An- 
other rather  recent  addition  to  the  black  list  is  the  house  fly  or 
typhoid  fly.  We  shall  see  later  with  what  reason  this  name 
is  given.  The  development  of  the  typhoid  fly  is  extremely 
rapid.  A  female  may  lay  from  one  hundred  to  two  hundred 
eggs.     These  are  usually  deposited  in  filth  or  manure.     Dung  heaps 


Life  history  of  house  flies,  showing  from  left  to  right  the  eggs,  larvse, 
pupse,  and  adult  flies.     (Photograph,  about  natural  size,  by  Overton.) 


THE  ECONOMIC   IMPORTANCE  OF  ANIMALS    223 


The  foot  of  a  fly,  showing  the 
hooks,  hairs,  and  pads 
which  collect  and  carry 
bacteria.  The  fly  doesn't 
wipe  his  feet. 


about  stables,  privy  vaults,  ash  heaps,  uncared-for  garbage  cans, 
a.nd  fermenting  vegetable  refuse  form  the  best  breeding  places  for 
flies.  In  warm  weather,  the  eggs  hatch  a 
day  or  so  after  they  are  laid  and  become 
larvae,  called  maggots.  After  about  one 
week  of  active  feeding,  these  wormlike 
maggots  become  quiet  and  go  into  the 
pupal  stage,  whence  under  favorable  con- 
ditions they  emerge  within  less  than  an- 
other week  as  adult  flies.  The  adults 
breed  at  once,  and  in  a  short  summer  there 
may  be  over  ten  generations  of  flies.  This 
accounts  for  the  great  number.  Fortu- 
nately relatively  few  flies  survive  the 
winter.  The  membranous  wings  of  the 
adult  fly  appear  to  be  two  in  number,  a 
second  pair  being  reduced  to  tiny  knobbed 
hairs  called  balancers.  The  head  is  freely 
movable,  wuth  large  compound  eyes.  The  mouth  parts  form  a 
proboscis,  which  is  tonguelike,  the  animal  obtaining  its  food  by 
lapping  and  sucking.     The  foot  shows  a  wonderful  adaptation  for 

clinging  to  smooth  surfaces. 
Two  or  three  pads,  each  of 
which  bears  tubelike  hairs  that 
secrete  a  sticky  fluid,  are  found 
on  its  under  surface.  It  is  by 
this  means  that  the  fly  is  able 
to  walk  upside  down,  and  carry 
bacteria  on  its  feet. 

The  Typhoid  Fly  a  Pest.  — 
The  common  fly  is  recognized 
as  a  pest  the  world  over.  Flies 
have  long  been  known  to  spoil 


food  through  their  filtliy  habits, 
but  it  is  more  recently  that  the 

Colonies  of  bacteria  which  have  developed    ^         gerioUS  charge  of  spread  of 
in    a  culture  medium  upon   which  a  ♦^  .      , 

fly  was  allowed  to  walk.  diseases,  caused  by  bacteria,  has 


224    THE   ECONOMIC   IMPORTANCE  OF  ANIMALS 


II-    ilUUIIIIIIIIIIIil1lll|i-U!"  -It 

Showing  how  flies  may  spread  disease  by- 
means  of  contaminating  food. 


been  laid  at  their  door.  In  a 
recent  experiment  two  young 
men  from  the  Connecticut 
Agricultural  Station  found  that 
a  single  fly  might  carry  on  its 
feet  anywhere  from  500  to 
6,000,000  bacteria,  the  average 
number  being  over  1,200,000. 
Not  all  of  these  germs  are 
harmful,  but  they  might  easily 
include  those  of  typhoid  fever, 
tuberculosis,  summer  com- 
plaint, and  possibly  other 
diseases.  A  recent  pamphlet 
published  by  the  Merchants' 
Association  in  New  York  City 
shows  that  the  rapid  increase  of  flies  during  the  summer  months 
has  a  definite  correlation  with  the  increase  in  the  number  of  cases 
of  summer  complaint.  Observations  in  other  cities  seem  to  show 
the  increase  in  number  of  typhoid  cases  in  the  early  fall  is  due, 
in  part  at  least,  to  the  same 
cause.  A  terrible  toll  of  dis- 
ease and  death  may  be  laid  at 
the  door  of  the  typhoid  fly. 

Recently  the  stable  fly  has 
been  found  to  carry  the  dread 
disease  known  as  infantile 
paralysis. 

Remedies.  —  Cleanliness 
which  destroys  the  breeding 
place  of  flies,  the  frequent  re- 
moval and  destruction  of  gar- 
bage, rubbish,  and  manure, 
covering  of  all  food  when  not 
in  use  and  especially  the  care- 
ful screening  of  windows  and 
doors    during    the    breeding 


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There  were  329  t^T^hoid  cases  in  Jackson- 
ville, Florida,  in  1910,   158  in  1911,  87 
first    10    months  of  1912.     80  to  85 


in 


per  cent  of  outdoor  toilets  were  made  fly 
proof  during  winter  of  1910.  Account 
for  the  decrease  in  typhoid  after  the 
flies  were  kept  out  of  the  toilets. 


THE  ECONOMIC  IMPORTANCE   OF  ANIMALS    225 

season,  will  all  play  a  part  in  the  reduction  of  flies.     To  the  motto 
"  swat  the  fly  "  should  be  added,  '^ remove  their  breeding  places!" 

Other  Insect  Disease  Carriers.  —  Fleas  and  bedbugs  have  been 
recently  added  to  those  insects  proven  to  carry  disease  to  man. 
Bubonic  plague,  which  is  primarily  a  disease  of  rats,  is  un- 
doubtedly transmitted  from  the  infected  rats  to  man  by  the  fleas. 
Fleas  are  also  believed  to  transmit  leprosy  although  this  is  not 
proven. 

To  rid  a  house  of  fleas  we  must  first  find  their  breeding  places. 
Old  carpets,  the  sleeping  places  of  cats  or  dogs  or  any  dirty  un- 
swept  corner  may  hold  the  eggs  of  the  flea.  The  young  breed  in 
cracks  and  crevices,  feeding  upon  organic 
matter  there.  Eventually  they  come  to  live 
as  adults  on  their  warm-blooded  hosts,  cats, 
dogs,  or  man.  Evidently  destruction  of  the 
breeding  places,  careful  washing  of  all  in- 
fected areas,  the  use  of  benzine  or  gasoline  Flea  which  transmits  Bu- 
in  crevices  where  the  larvae  may  be  hid  are       ^^°^"  ^'^^"^  ^'^^^  "^* 

•^  ^  to  man. 

the  most  effective   methods  of  extermina- 
tion.    Pets  which  might  harbor  fleas  should  be  washed  frequently 
with  a  weak  (two  to  three  per  cent)  solution  of  creolin. 

Bedbugs  are  difficult  to  prove  as  an  agent  in  the  transmission  of 
disease  but  their  disgusting  habits  are  sufficient  reason  for  their 
extermination.  It  has  been  proven  by  experiment  that  they  may 
spread  typhoid  and  relapsing  fevers.  They  prefer  human  blood 
to  other  food  and  have  come  to  live  in  bedrooms  and  beds  because 
this  food  can  be  obtained  there.  They  are  extremely  difficult  to 
exterminate  because  their  flat  body  allows  them  to  hide  in  cracks 
out  of  sight.  Wooden  beds  are  thus  better  protection  for  them 
than  iron  or  brass  beds.  Boiling  water  poured  over  the  cracks 
when  they  breed  or  a  mixture  of  strong  corrosive  sublimate  four 
parts,  alcohol  four  parts  and  spirits  of  turpentine  one  part,  are 
effective  remedies. 

How  the  Harm  done  by  Insects  is  Controlled.  —  The  com- 
bating of  insects  is  directed  by  several  bodies  of  men,  all  of 
which  have  the  same  end  in  view.  These  are  the  Bureau  of 
Entomology   of  the   United   States  Department  of   Agriculture, 

HUNTER,    CIV.    BI. 15 


226     THE   ECONOMIC   IMPORTANCE   OF  ANIMALS    • 

the  various   state   experiment   stations,    and   medical   and   civic 
organizations. 

The  Bureau  of  Entomology  works  in  harmony  with  the  other 
divisions  of  the  Department  of  Agriculture,  giving  the  time  of  its 
experts  to  the  problems  of  controlling  insects  which,  for  good  or 
ill,  influence  man's  welfare  in  this  country.  The  destruction  of 
the  malarial  mosquito  and  control  of  the  typhoid  fly;  the  de- 
struction of  harmful  insects  by  the  introduction  of  their  natural 
enemies,  plant  or  animal ;  the  perfecting  of  the  honeybee  (see 
Hodge,  Nature  Study  and  Life,  page  240),  and  the  introduction  of 
new  species  of  insects  to  pollinate  flowers  not  native  to  this  country 
(see  Blastophaga,  page  43),  are  some  of  the  problems  to  which  these 
men  are  now  devoting  their  time. 

All  the  states  and  territories  have,  since  1888,  established  state 
experiment  stations,  which  work  in  cooperation  with  the  govern- 
ment in  the  war  upon  injurious  insects.  These  stations  are  often 
connected  with  colleges,  so  that  young  men  who  are  interested  in 
this  kind  of  natural  science  may  have  opportunity  to  learn  and  to 
help. 

The  good  done  by  these  means  directly  and  indirectly  is  very 
great.  Bulletins  are  published  by  the  various  state  stations  and 
by  the  Department  of  Agriculture,  most  of  which  may  be  obtained 
free.  The  most  interesting  of  these  from  the  high  school  stand- 
point are  the  Farmers'  Bulletins,  issued  by 
the  Department  of  Agriculture,  and  the 
Nature  Study  pamphlets  issued  by  the 
Cornell  University  in  New  York  state. 

Animals  Other  than  Insects  may  be  Dis- 
ease Carriers.  —  The  common  brown  rat  is 
an  example  of  a  mammal,  harmful  to  civi- 
lized man,  which  has  followed  in  his  foot- 

This  diagram  shows  how    ^tcps  all   over  the   world.     Starting  from 
bubonic  plague  is  carried    China,  it  Spread  to  eastem  Europe,  thence 

diagTam'.     ^''''^^'''  *^'   ^^    Western  Europe,   and   in   1775  it  had 

obtained  a  lodgment  in  this  country.  In 
seventy-five  years  it  reached  the  Pacific  coast,  and  is  now  fairly 
common  all  over  the  United  States,  being  one  of  the  most  prolific 


THE  ECONOMIC   IMPORTANCE   OF  ANIMALS     227 


of  all  mammals.  Rats  are  believed  to  carry  bubonic  plague,  the 
''  Black  Death  "  of  the  Middle  Ages,  a  disease  estimated  to  have 
killed  25,000,000  people  during  the  fourteenth  century.  The  rat, 
like  man,  is  susceptible  to  plague  ;  fleas  bite  the  rat  and  then  biting 
man  transmit  the  disease  to  him.  A  determined  effort  is  now  being 
made  to  exterminate  the  rat  because  of  its  connection  with 
bubonic  plague. 

Other  Parasitic  Animals  cause  Disease.  —  Besides  parasitic 
protozoans  other  forms  of  animals  have  been  found  that  cause 
disease.  Chief  among  these  are  certain  round  and  flat  worms, 
which  have  come  to  live  as  parasites  on  man  and  other  animals. 
A  one-sided  relationship  has  thus  come  into  existence  where  the 
worm  receives  its  living  from  the  host,  as  the  animal  is  called  on 
which  the  parasite  lives.  Consequently  the  parasite  frequently 
becomes  fastened  to  its  host  during  adult  life  and  often  is  reduced 
to  a  mere  bag  through  which  the  fluid  food  prepared  by  its  host  is 
absorbed.  Sometimes  a  complicated  life  history  has  arisen  from 
their  parasitic  habits.  Such  is  seen  in  the 
life  history  of  the  liver  fluke,  a  flatworm 
which  kills  sheep,  and  in  the  tapeworm. 

Cestodes  or  Tapeworms.  —  These  para- 
sites infest  man  and  many  other  vertebrate 
animals.  The  tapeworm  (Tcenia  solium) 
passes  through  two  stages  in  its  life  history, 
the  first  within  a  pig,  the  second  within  the 
intestine  of  man.  The  developing  eggs  are 
passed  off  with  wastes  from  the  intestine 
of  man.  The  pig,  an  animal  with  dirty 
habits,  may  take  in  the  worm  embryos 
with  its  food.  The  worm  develops  within 
the  intestine  of  the  pig,  but  soon  makes  its 
way  into  the  muscle  or  other  tissues.  It 
is  here  known  as  a  bladderworm.  If  man  eats  raw  or  undercooked 
pork  containing  these  w^orms,  he  may  become  a  host  for  the  tape- 
worm. Thus  during  its  complete  life  history  it  has  two  hosts. 
Another  common  tapeworm  parasitic  on  man  lives  part  of  its  life  as 
an  embryo  within  the  muscles  of  cattle.     The  adult  worm  consists 


The  life  cycle  of  a  tape- 
worm. (1)  The  eggs  are 
taken  in  with  filthy  food 
by  the  pig;  (2)  man 
eats  undercooked  pork 
by  means  of  which 
the  bladder  worm  (3)  is 
transferred  to  his  own 
intestine  (4). 


228    THE   ECONOMIC   IMPORTANCE   OF  ANIMALS 


of  a  round  headlike  part  provided  with  hooks,  by  means  of  which 
it  fastens  itself  to  the  wall  of  the  intestine.  This  head  now  buds 
off  a  series  of  segmentlike  structures,  which  are  practically  bags 
full  of  sperms  and  eggs.  These  structures,  called  proglottids, 
break  off  from  time  to  time,  thus  allowing  the  developing  eggs  to 
escape.  The  proglottids  have  no  separate  digestive  systems,  but 
the  whole  body  surface,  bathed  in  digested  food,  absorbs  it  and  is 
thus  enabled  to  grow  rapidly. 

Roundworms.  —  Still   other   wormlike   creatures  called  round- 
worms are  of  importance  to  man.    Some,  as  the  vinegar  eel  found 

in  vinegar,  or  the  pinworms  parasitic  in  the 
lower  intestine,  particularly  of  children,  do  little 
or  no  harm.  The  pork  worm  or  trichina,  how- 
ever, is  a  parasite  which  may  cause  serious 
injury.  It  passes  through  the  first  part  of  its 
existence  as  a  parasite  in  a  pig  or  other  verte- 
brate (cat,  rat,  or  rabbit),  where  it  lies,  covered 
within  a  tiny  sac  or  cyst,  in  the  muscles  of  its 
hosts.  If  raw  pork  containing  these  worms  is 
eaten  by  man,  the  cyst  is  dissolved  off  by  the 
action  of  the  digestive  fluids,  and  the  living 
trichina  becomes  free  in  the  intestine  of  man. 
Here  it  reproduces  and  the  young  bore  their  way 
through  the  intestine  walls  and  enter  the  muscles, 
causing  inflammation  there.  This  causes  a  pain- 
ful and  often  fatal  disease  known  as  trichinosis. 

The  Hookworm.  —  The  discovery  by  Dr.  C. 
W.  Stiles  of  the  Bureau  of  Animal  Industry, 
that  the  laziness  and  shiftlessness  of  the  "  poor  whites  "  of  the 
South  is  partly  due  to  a  parasite  called  the  hookworm,  reads  like 
a  fairy  tale. 

The  people,  largely  farmers,  become  infected  with  a  larval  stage 
of  the  hookworm,  which  develops  in  moist  earth.  It  enters  the 
body  usually  through  the  skin  of  the  feet,  for  children  and  adults 
alike,  in  certain  localities  where  the  disease  is  common,  go  bare- 
foot to  a  considerable  extent. 
A  complicated  journey  from  the  skin  to  the  intestine  now  fol- 


Trichinella  spiralis 
imbedded  in 
human  muscle. 
(After  Leuckart.) 


THE  ECONOMIC  IMPORTANCE  OF  ANIMALS    220 

lows,  the  larvae  passing  through  the  veins  to  the  heart,  from  there 
to  the  lungs ;  here  they  bore  into  the  air  passages  and  eventually 
work  their  way  by  way  of  the  windpipe  into  the  intestine.  One 
result  of  the  injury  of  the  lungs  is  that  many  thus  infected  are 
subject  to  tuberculosis.  The  adult  worms,  once  in  the  food  tube, 
fasten  themselves  and  feed  upon  the  blood  of  their  host  by  punc- 
turing the  intestine  wall.  The  loss  of  blood  from  this  cause  is 
not  sufficient  to  account  for  the  bloodlessness  of  the  person  in- 
fected, but  it  has  been  discovered  that  the  hookworm  pours  out  a 


A  family  suffering  from  hookworm. 


poison  into  the  wound  which  prevents  the  blood  from  clotting 
rapidly  (see  page  315) ;  hence  a  considerable  loss  of  blood  occurs 
from  the  wound  after  the  worm  has  finished  its  meal  and  gone  to 
another- part  of  the  intestine. 

The  cure  of  the  disease  is  very  easy;  thymol  is  given,  which 
weakens  the  hold  of  the  worm,  this  being  followed  l)y 
Epsom  salts.  For  years  a  large  area  in  the  South  undoubtedly 
has  been  retarded  in  its  development  by  this  parasite ;  hundreds  of 
millions  of  dollars  and  thousands  of  lives  have  been  needlessly 
saciificed. 


230    THE  ECONOMIC   IMPORTANCE   OF  ANIMALS 

"  The  hookworm  is  not  a  bit  spectacular :  it  doesn't  get  itseK  dis- 
cussed in  legislative  halls  or  furiously  debated  in  political  campaigns. 
Modest  and  unassuming,  it  does  not  aspire  to  such  dignity.  It  is  satis- 
fied simply  with  (1)  lowering  the  working  efficiency  and  the  pleasure  of 
Uving  in  something  like  two  hundred  thousand  persons  in  Georgia  and 
all  other  Southern  states  in  proportion ;  with  (2)  amassing  a  death  rate 
higher  than  tuberculosis,  pneumonia,  or  typhoid  fever;  with  (3)  stub- 
bornly and  quite  effectually  retarding  the  agricultural  and  industrial  de- 
velopment of  the  section ;  with  (4)  nullifying  the  benefit  of  thousands  of 
dollars  spent  upon  education ;  with  (5)  costing  the  South,  in  the  course  of 
a  few  decades,  several  hundred  millions  of  dollars.  More  serious  and 
closer  at  hand  than  the  tariff;  more  costly,  threatening,  and  tangible 
than  the  Negro  problem ;  making  the  menace  of  the  boll  weevil  laughable 
in  comparison  —  it  is  preeminently  the  problem  of  the  South."  —  Atlanta 
Constitution. 


Animals  that  prey  upon  Man.  —  The  toll  of  death  from  animals 
which  prey  upon  or  harm  man  directly  is  relatively  small.  Snakes 
in  tropical  countries  kill  many  cattle  and  not  a  few  people. 

The  bite  of  the  rattlesnake  of  our  own  country,  although  dangerous, 
seldom  kills.    The  dreaded  cobra  of  India  has  a  record  of  over  two  hundred 

and  fift}^  thousand  persons 
killed  in  the  last  thirtj^- 
five  years.  The  Indian 
government  yearly  pays 
out  large  sums  for  the  ex- 
termination of  venomous 
snakes,  over  two  hundred 
thousand  of  which  have 
been  killed  during  a  single 
year. 

Alligators  and  Croco- 
diles. —  These  feed  on 
fishes,  but  often  attack  large  animals,  as  horses,  cows,  and  even  man. 
They  seek  their  prey  chiefly  at  night,  and  spend  the  day  basking  in  the 
sun.  The  crocodiles  of  the  Ganges  River  in  India  levy  a  yearly  tribute 
of  many  hundred  lives  from  the  natives. 

Carnivorous  animals  such  as  lions  and  tigers  still  inflict  damage 
in  certain  parts  of  the  world,  but  as  the  tide  of  civilization  ad- 


A  flesh-eating  reptile,  the  alligator. 


THE   ECONOMIC   IMPORTANCE   OF  ANIMALS     231 

vances,  their  numbers  are  slowly  but  surely  decreasing  so  that  as 
important  factors  in  man's  welfare  they  may  be  considered  almost 
negligible. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Beebe,  The  Bird.     Henry  Holt  and  Company. 

Bigelow,  Applied  Biology.       Macmillan  and  Company 

Davison,  Practical  Zoology.     American  Book  Company. 

Herrick,  Household  Insects  and  Methods  of  Control.     Cornell  Reading  Courses. 

Hornaday,  Our  Vanishing  Wild  Life.     New  York  Zoological  Society. 

Hodge,  Nature  Study  and  Life.     Ginn  and  Company. 

Kipling,  Captains  Courageous.     Charles  Scribner's  Sons. 

Sharpe,  Laboratory  Manual,  pp.    157-158,    182-203,   320-341.      American    Book 

Company. 
Stone  and  Cram,  American  Animals.     Doubleday,  Page  and  Company, 
Toothaker,  Commercial  Raw  Materials.     Ginn  and  Company. 

ADVANCED 

Flower,  The  Horse.     D.  Appleton  and  Company. 

Hornaday,  The  American  Natural  History.     Macmillan  and  Company. 

Jordan,  Fishes.     Henry  Holt  and  Company. 

Jordan  and  Evermann,    American  Food  and  Game  Fishes.     Doubleday,  Page   and 

Company. 
Schaler,  Domesticated  Animals,  their  Relations  to  Man  and  to  His  Advancement  in 

Civilization.     Charles  Scribner's  Sons. 


XVI.  THE  FISH  AND  FROG,  AN  INTRODUCTORY 
STUDY  OF  VERTEBRATES 

Problems,  —  To  determine  how  a  fish  and  a  frog  are  fitted 
for  the  life  they  lead. 

To  determine  some  methods  of  development  in  vertebrate 
animals. 

{a)  Fishes. 

Q))   Frogs. 

(c)    Other  aniinals. 

Laboratory  Suggestions 

Laboratory  exercise.  —  Study  of  a  living  fish  —  adaptations  for  pro- 
tection, locomotion,  food  getting,  etc. 

Laboratory  demonstration.  —  The  development  of  the  fish  or  frog  Oi^g. 

Visit  to  the  aquarium.  —  Study  of  adaptations,  economic  uses  of  fishes, 
artificial  propagation  of  fishes. 

Two  Methods  of  Breathing  in  Vertebrates.  —  Vertebrate 
animals  have  at  least  two  methods  of  getting  their  oxygen.  In 
other  respects  their  life  processes  are  nearly  similar.  Of  all 
vertebrates  fishes  are  the  only  ones  fitted  to  breathe  all  their  lives 
under  water.  Other  vertebrates  are  provided  with  lungs  and 
take  their  oxygen  directly  from  the  air.^  We  will  next  take  up 
the  study  of  a  fish  to  see  how  it  is  fitted  for  its  life  in  the  water. 

STUDY  OF  A   FISH 

The  Body.  —  One  of  our  common  fresh-water  fish  is  the  bream, 
or  golden  shiner.  The  body  of  the  bream  runs  insensibly  into  the 
head,  the  neck  being  absent.  The  long,  narrow  body  with  its 
smooth  surface  fits  the  fish  admirably  for  its  life  in  the  water. 
Certain  cells  in  the  skin  secrete  mucus  or  slime,  another  adapta- 

1  With  the  exception  of  a  few  lungless  salamanders.  Most  salamanders  get  nQiicb 
of  their  supply  of  oxygen  through  their  moist  skins- 

232 


THE   FISH  233 

tion.  The  position  of  the  scales,  overlapping  in  a  backward  di- 
rection, is  yet  another  adaptation  which  aids  in  passing  through 
the  water.  Its  color,  olive  above  and  bright  silver  and  gold  below, 
is  protective.     Can  you  see  how  ? 


The  bream.     A,  dorsal  fin ;  B,  caudal  fin  ;  C,  anal  fin  ;  D,  pelvic  fin  ; 

E,  pectoral  fin. 

The  Appendages  and  their  Uses.  —  The  appendages  of  the  fish 
consist  of  paired  and  unpaired  fins.  The  paired  fins  are  four  in 
number,  and  are  believed  to  correspond  in  position  and  structure 
with  the  paired  limbs  of  a  man.  Note  the  illustration  above 
and  locate  the  paired  pectoral  and  pelvic  fins.  (These  are  so  called 
because  they  are  attached  to  the  bones  forming  the  pectoral  and 
pelvic  girdles.  (See  page  268.)  Find,  by  comparison  with  the 
Figure,  the  dorsal,  anal,  and  caudal  fins.  How  many  unpaired 
fins  are  there? 

The  flattened,  muscular  body  of  the  fish,  tapering  toward  the 
caudal  fin,  is  moved  from  side  to  side  with  an  undulating  motion 
which  results  in  the  forward  movement  of  the  fish.  This  move- 
ment is  almost  identical  with  that  of  an  oar  in  sculling  a  boat. 
Turning  movements  are  brought  about  by  use  of  the  lateral  fins 
in  much  the  same  way  as  a  boat  is  turned.  We  notice  the  dorsal 
and  other  single  fins  are  evidently  useful  in  balancing  and  steer- 
ing. 

The  Senses.  —  The  position  of  the  eyes  at  the  side  of  the  head 
is  an  evident  advantage  to  the  fish.     Why?    The  eye  is  globular 


234  A   STUDY  OF   VERTEBRATES 

in  shape.  Such  an  eye  has  been  found  to  be  very  nearsighted. 
Thus  it  is  unlikely  that  a  fish  is  able  to  perceive  objects  at  any 
great  distance  from  it.  The  eyes  are  unprotected  by  eyelids,  but 
the  tough  outer  covering  and  their  position  afford  some  protection. 

Feeding  experiments  with  fishes  show  that  a  fish  becomes  aware 
of  the  presence  of  food  by  smelling  it  as  well  as  by  seeing  it.  The 
nostrils  of  a  fish  can  be  proved  to  end  in  little  pits,  one  under  each 
nostril  hole.  Thus  they  differ  from  our  own,  which  are  connected 
with  the  mouth  cavity.  In  the  catfish,  for  example,  the  barbels, 
or  horns,  receive  sensations  of  smell  and  taste.  They  do  not 
perceive  odors  as  we  do  for  a  fish  perceives  only  substances  that 
are  dissolved  in  the  water  in  which  it  lives.  The  senses  of  taste 
and  touch  appear  to  be  less  developed  than  the  other  senses. 

Along  each  side  of  mpst  fishes  is  a  line  of  tiny  pits,  provided  with 
sense  organs  and  connected  with  the  central  nervous  system  of  the 
fish.  This  area,  called  the  lateral  line,  is  believed  to  be  sensitive 
to  mechanical  stimuli  of  certain  sorts.  The  ''  ear  "  of  the  fish  is 
under  the  skin  and  serves  partly  as  a  balancing  organ. 

Food  Getting. — A  fish  must  go  after  its  food  and  seize  it,  but 
has  no  structures  for  grasping  except  the  teeth.  Consequently 
we  find  the  teeth  small,  sharp,  and  numerous,  well  adapted  for 
holding  living  prey.  The  tongue  in  most  fishes  is  wanting  or 
very  slightly  developed. 

Breathing.  —  A  fish,  when  swimming  quietly  or  when  at  rest, 
seems  to  be  biting  when  no  food  is  present.  A  reason  for  this  act 
is  to  be  seen  when  we  introduce  a  little  finely  powdered  carmine 
into  the  water  near  the  head  of  the  fish.  It  will  be  found  that  a 
current  of  water  enters  the  mouth  at  each  of  these  biting  move- 
ments and  passes  out  through  two  slits  found  on  each  side  of  the 
head  of  the  fish.  Investigation  shows  us  that  under  the  broad,  flat 
plate,  or  operculum,  forming  each  side  of  the  head,  lie  several  long, 
feathery,  red  structures,  the  gills. 

Gills.  —  If  we  examine  the  gills  of  any  large  fish,  we  find  that  a 
single  gill  is  held  in  place  by  a  bony  arch,  made  of  several  pieces 
of  bone  which  are  hinged  in  such  a  way  as  to  give  great  flexibility 
to  the  gill  arch,  as  the  support  is  called.  Covering  the  bony 
framework,  and  extending  from  it,  are  numerous  delicate  filaments 


THE   FISH 


235 


J^ 


H 


Diagram  of  the  gills  of  a  fish.  (H),  the 
heart  which  forces  the  blood  into  the 
tubes  (F),  which  run  out  into  the  gill 
filaments.  A  gill  bar  (G)  supports 
each  gill.  The  blood  after  exchang- 
ing its  carbon  dioxide  for  oxygen  is 
sent  out  to  the  cells  of  the  body 
through  the  artery  (A). 


covered  with  a  very  thin  membrane  or  skin.  Into  each  of  these 
filaments  pass  two  blood  vessels ;  in  one  blood  flows  downward  and 
in  the  other  upward.  Blood 
reaches  the  gills  and  is  carried 
away  from  these  organs  by 
means  of  two  large  vessels  which 
pass  along  the  bony  arch  pre- 
viously mentioned.  In  the  gill 
filament  the  blood  comes  into 
contact  with  the  free  oxygen  of 
the  water  bathing  the  gills.  An 
exchange  of  gases  through  the 
walls  of  the  gill  filaments  results 
in  the  loss  of  carbon  dioxide 
and  a  gain  of  oxygen  by  the 
blood.  The  blood  carries  oxy- 
gen to  the  cells  of  the  body 
and  (as  work  is  done  by  the 
cells  as  a  result  of  the  oxidation  of  food)  brings  carbon  dioxide 
back  to  the  gills. 

Gill  Rakers.  —  If  we  open  wide  the  mouth  of  any  large  fish  and 
look  inward,  we  find  that  the  mouth  cavity  leads  to  a  funnel-like 
opening,  the  gullet.  On  each  side  of  the  gullet  we  can  see  the  gill 
arches,  guarded  on  the  inner  side  by  a  series  of  sharp-pointed  struc- 
tures, the  gill  rakers.  In  some  fishes  in  which  the  teeth  are  not 
well  developed,  there  seems  to  be  a  greater  development  of  the 
gill  rakers,  which  in  this  case  are  used  to  strain  out  small  organisms 
from  the  water  which  passes  over  the  gills.  Many  fishes  make 
such  use  of  the  gill  rakers.  Such  are  the  shad  and  menhaden, 
which  feed  almost  entirely  on  plankton,  a  name  given  to  the 
small  organisms  found  by  millions  near  the  surface  of  water. 

Digestive  System.  —  The  gullet  leads  directly  into  a  baglike  stomach. 
There  are  no  salivary  glands  in  the  fishes.  There  is,  however,  a  large 
liver,  which  appears  to  be  used  as  a  digestive  gland.  This  organ,  because 
of  the  oil  it  contains,  is  in  some  fishes,  as  the  cod,  of  considerable  economic 
importance.  Many  fishes  have  outgrowths  like  a  series  of  pockets  from 
the  intestine.     These  structures,  called  the  pyloric  cceca,  are  believed  to 


236 


A   STUDY    OF   VERTEBRATES 


secrete  a  digestive  fluid.  The  intestine  ends  at  the  vent,  which  is  usually 
located  on  the  under  side  of  the  fish,  immediately  in  front  of  the  anal  fin. 
Swim  Bladder.  —  An  organ  of  unusual  significance,  called  the  swim 
bladder,  occupies  the  region  just  dorsal  to  the  food  tube.  In  young  fishes 
of  many  species  this  is  connected  by  a  tube  with  the  anterior  end  of  the 
digestive  tract.  In  some  fonns  this  tube  persists  throughout  life,  but  in 
other  fishes  it  becomes  closed,  a  thin,  fibrous  cord  taking  its  place.  The 
swim  bladder  aids  in  giving  the  fish  nearly  the  same  weight  as  the  water 


a  H 


A  fish  opened  to  show  H,  the  heart ;  G,  the  gills  ;  L,  the  liver ;  S,  the  stoinach  ; 
/,  the  intestine ;  0,  the  ovary ;  K,  the  kidney,  and  B,  the  air  bladder. 

it  displaces,  thus  buoying  it  up.  The  walls  of  the  organ  are  richly  sup- 
plied with  blood  vessels,  and  it  thus  undoubtedly  serves  as  an  organ  for 
supplying  oxygen  to  the  blood  when  all  other  sources  fail.  In  some 
fishes  (the  dipnoi,  page  187)  it  has  come  to  be  used  as  a  lung. 

Circulation  of  the  Blood.  —  In  the  vertebrate  animals  the  blood  is 
said  to  circulate  in  the  body,  because  it  passes  through  a  more  or  less  closed 
system  of  tubes  in  its  course  around  the  body.  In  the  fishes  the  heart  is 
a  two-chambered  muscular  organ,  a  thin-walled  auricle,  the  receiving 
chamber,  leading  into  a  thick-walled  muscular  ventricle  from  which  the 
blood  is  forced  out.  The  blood  is  pumped  from  the  heart  to  the  gills; 
there  it  loses  some  of  its  carbon  dioxide ;  it  then  passes  on  to  other  parts 
of  the  body,  eventually  breaking  up  into  very  tiny  tubes  called  capillaries. 
From  the  capillaries  the  blood  returns,  in  tubes  of  gradually  increasing 
chameter,  toward  the  heart  again.  The  body  cells  lie  between  the  smallest 
branches  of  the  capillaries.  Thus  they  get  from  the  blood  food  and  oxy- 
gen and  return  to  the  blood  the  wastes  resulting  from  oxidation  within 
the  cell  body.  During  its  course  some  of  the  blood  passes  through  the 
kidneys  and  is  there  reheved  of  part  of  its  nitrogenous  waste.     Circulation 


THE  FISH  237 

of  blood  in  the  body  of  the  fish  is  rather  slow.  The  temperature  of  the 
blood  being  nearly  that  of  the  surrounding  media  in  which  the  fish  fives, 
the  animal  has  incorrectly  been  given  the  term  "  cold-blooded." 

Nervous  System.  —  As  in  all  other  vertebrate  animals,  the  brain  and 
spinal  cord  of  the  fish  are  partially  inclosed  in  bone.  The  central  nervous 
system  consists  of  a  brain,  with  nerves  connecting  the  organs  of  sight, 
taste,  smell,  and  hearing,  and  such  parts  of  the  body  as  possess  the  sense  of 
touch ;  a  spinal  cord ;  and  spinal  nerves.  Nerve  cells  located  near  the  out- 
side of  the  body  send  in  messages  to  the  central  system,  which  are  there 
received  as  sensations.  CeUs  of  the  central  nervous  system,  in  turn,  send 
out  messages  which  result  in  the  movement  of  muscles. 

Skeleton.  —  In  the  vertebrates,  of  which  the  bonj^  fish  is  an  example, 
the  skeleton  is  under  the  skin,  and  is  hence  called  an  endoskeleton.  It 
consists  of  a  bony  framework,  the  vertebral  column  which  protects  the 
spinal  cord  and  certain  attached  bones,  the  ribs,  with  other  spiny  bones  to 
which  the  unpaired  fins  are  attached.  The  paired  fins  are  attached  to  the 
spinal  column  by  two  collections  of  bones,  known  respectively  as  the 
pectoral  and  pelvic  girdles.  The  bones  in  the  main  skeleton  serve  in  the 
fish  for  the  attachment  of  powerful  muscles,  by  means  of  which  locomo- 
tion is  accomplished.  In  most  fishes,  the  exoskeleton,  too,  is  well  developed, 
consisting  usually  of  scales,  but  sometimes  of  bony  plates. 

Food  of  Fishes.  —  We  have  already  seen  that  in  a  balanced 
aquarium  the  balance  of  food  was  preserved  by  the  plants,  which 
furnished  food  for  the  tiny  animals  or  were  eaten  by  larger  ones,  — 
for  example,  snails  or  fish.  The  smaller  animals  in  turn  became 
food  of  larger  ones.  The  nitrogen  balance  was  maintained  through 
the  excretions  of  the  animals  and  their  death  and  decay. 

The  marine  world  is  a  great  balanced  aquarium.  The  upper 
layer  of  water  is  crowded  with  all  kinds  of  little  organisms,  both 
plant  and  animal.  Some  of  these  are  microscopic  in  size ;  others, 
as  the  tiny  crustaceans,  are  visible  to  the  eye.  On  these  little 
organisms  some  fish  feed  entirely,  others  in  part.  Such  are  the 
menhaden  1  (bony,  bunker,  mossbunker  of  our  coast),  the  shad, 
and  others.     Other  fishes  are  bottom  feeders,  as  the  blackfish  and 

1  It  has  been  discovered  by  Professor  Mead  of  Brown  University  that  the  in- 
crease in  starfish  along  certain  parts  of  the  New  England  coast  was  in  part  due 
to  overfishing  of  menhaden,  which  at  certain  times  in  the  year  feed  almost  entirely 
on  the  young  starfish. 


238 


A   STUDY    OF   VERTEBRATES 


the  sea  bass,  living  almost  entirely  upon  mollusks  and  crusta- 
ceans. Still  others  are  hunters,  feeding  upon  smaller  species  of 
fish,  or  even  upon  their  weaker  brothers.  Such  are  the  bluefish. 
squeteague  or  weakfish,  and  others. 

What  is  true  of  salt-water  fish  is  equally  true  of  those  inhabiting 
our  fresh-water  streams  and  lakes.  It  is  one  of  the  greatest  prob- 
lems of  our  Bureau  of  Fisheries  to  discover  this  relation  of  various 
fishes  to  their  food  supplies  so  as  to  aid  in  the  conservation  and 
balance  of  life  in  our  lakes,  rivers,  and  seas. 

Migration  of  Fishes.  —  Some  fishes  change  their  habitat  at  dif- 
ferent times  during  the  year,  moving  in  vast  schools  northward 
in  summer  and  southward  in  the  winter.  In  a  general  way  such 
migrations  follow  the  coast  lines.  Examples  of  such  migratory 
fish  are  the  cod,  menhaden,  herring,  and  bluefish.  The  migra- 
tions are  due  to  temperature  changes,  to  the  seeking  after  food, 
and  to  the  spawning  instinct.  Some  fish  migrate  to  shallower 
water  in  the  summer  and  to  deeper  water  in  the  winter ;   here  the 

reason  for  the  migra- 
tion is  doubtless  the 
change  in  temperature. 
The  Egg-laying 
Habits  of  the  Bony 
Fishes.  —  The  eggs  of 
most  bony  fishes  are 
laid  in  great  numbers, 
varying  from  a  few 
thousand  in  the  trout 
to  many  hundreds  of 
thousands  in  the  shad 
and  several  millions  in 
the  cod.  The  time  of 
egg-laying  is  usually 
spring  or  early  sum- 
mer. At  the  time  of 
spawning  the  male 
usually  deposits  milt,  consisting  of  millions  of  sperm  cells,  in  the 
water  just  over  the  eggs,  thus  accomplishing  fertilization.     Some 


Development  of  a  trout.  1,  the  embryo  within  the 
egg  ;  2,  the  young  fish  just  hatched  with  the  yoke 
sac  still  attached  ;  3,  the  young  fish. 


THE  FISH  239 

fishes,  as  sticklebacks,  sunfish,  toadfish,  etc.,  make  nests,  but 
visually  the  eggs  are  left  to  develop  by  themselves,  sometimes 
attached  to  some  submerged  object,  but  more  frequently  free  in 
the  water.  In  some  eggs  a  tiny  oil  drop  buoys  up  the  egg  to  the 
surface,  where  the  heat  of  the  sun  aids  development.  They  are 
exposed  to  many  dangers,  and  both  eggs  and  developing  fish  are 
eaten,  not  only  by  birds,  fish  of  other  species,  and  other  water  in- 
habitants, but  also  by  their  own  relatives,  and  even  parents. 
Consequently  a  very  small  percentage  of  eggs  ever  produce  ma- 
ture fish. 

The  Relation  of  the  Spawning  Habits  to  Economic  Importance 
of  Fish.  —  The  spawning  habits  of  fish  are  of  great  importance  to 
us  because  of  the  economic  value  of  fish  to  mankind,  not  only 
directly  as  a  food,  but  indirectly  as  food  for  other  animals  in  turn 
valuable  to  man.  Many  of  our  most  desirable  food  fishes,  notably 
the  salmon,  shad,  sturgeon,  and  smelt,  pass  up  rivers  from  the 
ocean  to  deposit  their  eggs,  swimming  against  strong  currents 
much  of  the  way,  some  species  leaping  rapids  and  falls,  in  order 
to  deposit  their  eggs  in  localities  where  the  conditions  of  water 
and  food  are  suitable,  and  the  water  shallow  enough  to  allow 
the  sun's  rays  to  warm  it  sufficiently  to  cause  the  eggs  to  develop. 
The  Chinook  salmon  of  the  Pacific  coast,  the  salmon  used  in  the 
Western  canning  industry,  travels  over  a  thousand  miles  up  the 
Columbia  and  other  rivers,  where  it  spa^vns.  The  salmon  begin 
to  pass  up  the  rivers  in  early  spring,  and  reach  the  spav/ning  beds, 
shallow  deposits  of  gravel  in  cool  mountain  streams,  before  late 
summer.  Here  the  fish,  both  males  and  females,  remain  until 
the  temperature  of  the  water  falls  to  about  54°  Fahrenheit.  The 
eggs  and  milt  are  then  deposited,  and  the  old  fish  die,  leaving  the 
eggs  to  be  hatched  out  later  by  the  heat  of  the  sun's  rays. 

Need  of  Conservation.  — The  instinct  of  this  and  other  species 
of  fish  to  go  into  shallow  rivers  to  deposit  their  eggs  has  been 
made  use  of  by  man.  At  the  time  of  the  spawning  migration  the 
salmon  are  taken  in  vast  numbers,  for  the  salmon  fisheries  net 
over  $16,000,000  annually. 

But  the  need  for  conservation  of  this  important  national  asset 
is  great.     The  shad  have  within  recent  time  abandoned   their 


240 


A   STUDY   OF   VERTEBRATES 


breeding  places  in  the  Connecticut  River,  and  the  salmon  have  been 
exterminated  along  our  eastern  coast  within  the  past  few  decades. 
It  is  only  a  matter  of  a  few  years  when  the  Western  salmon  will 
be  extinct  if  fishing  is  continued  at  the  present  rate.  More  fish 
must  be  allowed  to  reach  their  breeding  places.  To  do  this  a 
closed  season  on  the  rivers  of  two  or  three  days  out  of  each  seven 
while  the  shad  or  the  salmon  run  would  do  much  good. 

The  sturgeon,  the  eggs  of  which  are  used  in  the  manufacture  of 
the  delicacy  known  as  caviar,  is  an  example  of  a  fish  that  is  almost 
extinct  in  this  part  of  the  world.  Other  food  fish  taken  at  the 
breeding  season  are  also  in  danger. 

Artificial  Propagation  of  Fishes.  —  Fortunately,  the  govern- 
ment through  the  Bureau  of  Fisheries,  and  various  states  by  wise 
protective  laws  and  by  artificial  propagation  of  fishes,  are  be- 
ginning to  turn  the  tide.  Certain  days  of  the  week  the  salmon 
are  allowed  to  pass  up  the  Columbia  unmolested.  Closed  breed- 
ing seasons  protect  our  trout,  bass,  and  other  game  fish,  also  the 

catching  of  fish   under 


a    certain    size   is  pro- 
hibited. 

Many  fish  hatcheries, 
both  government  and 
state,  are  engaged  in 
artificially  fertilizing 
millions  of  fish  eggs  of 
various  species  and  pro- 
tecting the  young  fry 
until  they  are  of  such 
size  that  they  can  take 
care  of  themselves,  when  they  are  placed  in  ponds  or  streams. 
This  artificial  fertilization  is  usually  accomplished  by  first  squeezing 
out  the  ripe  eggs  from  a  female  into  a  pan  of  water ;  in  a  similar 
mamier  the  milt  or  sperm  cells  are  obtained,  and  poured  over  the 
eggs.  The  eggs  are  thus  fertilized.  They  are  then  placed  in  re- 
ceptacles supplied  with  running  water  and  left  to  develop  under 
favorable  conditions.  Shortly  after  the  egg  has  segmented  (divided 
into  many  cells)  the  embryo  may  be  seen  developing  on  one  side 


Artificial  fertilization  of  fish  eggs. 


THE  FROG  241 

of  the  egg.  The  rest  of  the  egg  is  made  up  of  food  or  yolk, 
and  when  the  baby  fish  hatches  it  has  for  some  time  the  yolk 
attached  to  its  ventral  surface.  Eventually  the  food  is  absorbed 
into  the  body  of  the  fish.  The  development  of  the  fish  is  direct, 
the  young  fish  becoming  an  adult  without  any  great  change  in 
form.  The  young  fry  are  kept  under  ideal  conditions  until  later, 
when  they  are  shipped,  sometimes  thousands  of  miles,  to  their 
new  homes. 

Early  development  of  salmon.     Natural  size. 

Note  to  Teacher.  —  It  is  suggested  that  in  the  spring  term  the  frog  be  studied, 
but  if  animal  biology  be  taken  up  during  the  fall  term  the  fish  only  might  be  used. 


THE   FROG 

Adaptations  for  Life.  —  The  most  common  frog  in  the  eastern 
part  of  the  United  States  is  the  leopard  frog.  It  is  recognized  by 
its  greenish  brown  body  with  dark  spots,  each  spot  being  outlined 
in  a  lighter-colored  background.  In  spite  of  the  apparent  lack  of 
harmony  with  their  surroundings,  their  color  appears  to  give 
almost  perfect  protection.  In  some  species  of  frogs  the  color  of 
the  skin  changes  with  the  surroundings  of  the  frog,  another  means 
of  protection. 

Adaptations  for  life  in  the  water  are  numerous.  The  ovoid 
body,  the  head  merging  into  the  trunk,  the  slimy  covering  (for 
the  frog  is  provided,  like  the  fish,  with  mucus  cells  in  the  skin), 
and  the  powerful  legs  with  webbed  feet,  are  all  evidences  of  the 
life  which  the  frog  leads. 

Locomotion.  —  You  will  notice  that  the  appendages  have  the 
same  general  position  on  the  body  and  same  number  of  parts  as 
do  your  own  (upper  arm,  forearm,  and  hand ;  thigh,  shank,  and 
foot,  the  latter  much  longer  relatively  than  your  own).  Note  that 
while  the  hand  has  four  fingers,  the  foot  has  five  toes,  the  latter 
connected  by  a  web.     In  swimming  the  frog  uses  the  stroke  we 

HUNTER,    CIV.    BI. 16 


242 


A   STUDY   OF   VERTEBRATES 


all  aim  to  make  when  we  arc  learning  to  swim.  Most  of  the  energy 
is  liberated  from  the  powerful  backward  •  push  of  the  hind  legs, 
which  in  a  resting  position  are  held  doubled  up  close  to  the  body. 
On  land,  locomotion  may  be  by  hopping  or  crawling. 

Sense  Organs.  —  The  frog  is  well  provided  with  sense  organs. 
The  eyes  are  large,  globular,  and  placed  at  the  side  of  the  head. 
When  they  are  closed,  a  delicate  fold,  or  third  eyelid,  called  the 
nictitating  memhrane,  is  drawn  over  each  eye.  Frogs  probably 
see  best  moving  objects  at  a  few  feet  from  them.  Their  vision  is 
much  keener  than  that  of  the  fish.  The  external  ear  (tympanum) 
is  located  just  behind  the  eye  on  the  side  of  the  body.  Frogs  hear 
sounds  and  distinguish  various  calls  of  their  own  kind,  as  is  proved 
by  the  fact  that  frogs  recognize  the  warning  notes  of  their  mates 

when  any  one  is  approaching.  The  inner  ear 
also  has  to  do  with  balancing  the  body  as  it  has 
in  fishes  and  other  vertebrates.  Taste  and  smell 
are  probably  not  strong  sensations  in  a  frog  or 
toad.  They  bite  at  moving  objects  of  almost 
any  kind  when  hungry.  The  long  flexible 
tongue,  which  is  fastened  at  the  front,  is  used  to 
catch  insects.  Experience  has  taught  these 
animals  that  moving  things,  insects,  worms,  and 
the  like,  make  good  food.  These  they  swallow 
whole,  the  tiny  teeth  being  used  to  hold  the 
food.  Touch  is  a  well-developed  sense.  They 
also  respond  to  changes  in  temperature  under 
water,  remaining  there  in  a  dormant  state  for 
^, .     ,.  ,         the    winter  when   the  temperature  of   the  air 

Inis  diagram  snows  ^ 

how  the  frog  uses  becomes  colder  than  that  of  the  water. 

its  tongue  to  catch       Breathing.  —  The   frog   breathes   by    raising 

and  lowering  the  floor  of  the  mouth,  pulling 
in  air  through  the  two  nostril  holes.  Then  the  little  flaps  over 
the  holes  are  closed,  and  the  frog  swallows  this  air,  forcing  it 
down  into  the  baglike  lungs.  The  skin  is  provided  with  many 
tiny  blood  vessels,  and  in  winter,  while  the  frogs  are  dormant 
at  the  bottom  of  the  ponds,  it  serves  as  the  only  organ  of  respi- 
ration. 


THE  FROG 


243 


The  Food  Tube  and  its  Glands.  —  Tho  mouth  loads  liko  a  funnel 
into  a  short  tube,  tho  gdllel.  On  the  lower  floor  of  the  mouth  can 
be  seen  the  slitlike  glottis  leading  to  the  lungs.  The  guUot  widens 
almost  at  once  into  a  long  stomach,  which  in  turn  loads  into  a  much 
coiled  intestine.  This  widens  abruptly  at  tho  lower  end  to  form 
the  large  intestine.  The  latter  leads  into  the  cloaca  (Latin, 
sewer),  into  which  open  the  kidneys,  urinary  bladder,  and  repro- 
ductive organs  (ovaries  or  spermaries).  Several  glands,  the  func- 
tion of  which  is  to  produce  digestive  fluids,  open  into  the  food 
tube.  These  digestive  fluids,  by  means  of  the  ferments  or  enzymes 
contained  in  them,  change  insoluble  food 
materials  into  a  soluble  form.  This  allows 
of  the  absorption  of  food  material  through 
the  walls  of  the  food  tube  into  the  blood. 
The  glands  (having  the  same  names  and 
uses  as  those  in  man)  are  the  sali- 
vary glands,  which  pour  their  juices 
into  the  mouth,  the  gastric  glands 
in  the  walls  of  the  stom- 
ach, and  the  liver  and 
pancreas,  which  open 
into  the  intestine. 

Circulation.  —  The  frog 
has  a  well-developed  heart, 
composed  of  a  thick-walled 
muscular  ventricle  and  two 
thin-walled  auricles.  The 
heart  pumps  the  blood 
through  a  system  of  closed 
tubes  to  all  parts  of  the 
body.  Blood  enters  the  internal  organs  of  a  frog:  M,  mouth;  T,  tongue;  Lu. 
right  auricle  from  all  parts  lungs;    H,  heart;    St,  stomach;    I,  small  intes- 

f  ,1       1      1         •,    ,1  tine;,  L,  liver;  G.  gallbladder;  P,  pancreas;  C, 

of  the  body ;    it  then  con-         ^^^^;^.  ^  ^^.^^^^  ^^^^^^^  .  g,  ^pieen;  K.  kidney. 

tains    considerable    carbon  Od,    oviduct;    O,  ovary;    Br,   brain;    Sc;   spinal 

dioxide;   the  blood  enter-        cord;  Ba,  back  bone. 

ing  the  left  auricle  comes 

from  the  lungs,  hence  it  contains  a  considerable  amount  of  oxygen.     Blood 

leaves  the  heart  through  the  ventricle,  which  thus  pumps  some  blood 


244  A  STUDY  OF  VERTEBRATES 

containing  much  and  some  containing  little  oxygen.  Before  the  blood 
from  the  tissues  and  lungs  has  time  to  mix,  however,  it  leaves  the  ventricle 
and  by  a  deUcate  adjustment  in  the  vessels  leaving  the  heart  most  of  the 
blood  containing  much  oxygen  is  passed  to  all  the  various  organs  of  the 
body,  while  the  blood  deficient  in  oxygen,  but  containing  a  large  amount 
of  carbon  dioxide,  is  pumped  to  the  lungs,  where  an  exchange  of  oxygen 
and  carbon  dioxide  takes  place  by  osmosis. 

In  the  tissues  of  the  body  wherever  work  is  done  the  process  of  burning 
or  oxidation  must  take  place,  for  by  such  means  only  is  the  energy  neces- 
sary to  do  the  work  released.  Food  in  the  blood  is  taken  to  the  muscle 
cells  or  other  cells  of  the  body  and  there  oxidized.  The  products  of  the 
burning  —  carbon  dioxide  —  and  any  other  organic  wastes  given  off  from 
the  tissues  must  be  eliminated  from  the  body.  As  we  know,  the  carbon 
dioxide  passes  off  through  the  lungs  and  to  some  extent  through  the  skin 
of  the  frog,  while  the  nitrogenous  wastes,  poisons  which  must  be  taken 
from  the  blood,  are  eliminated  from  it  in  the  kidneys. 

Change  of  Form  in  Development  of  the  Frog.  —  Not  all  verte- 
brates develop  directly  into  an  adult.  The  frog,  for  example, 
changes  its  form  completely  before  it  becomes  an  adult.  This 
change  in  form  is  known  as  a  metamorphosis.  Let  us  examine 
the  development  of  the  common  leopard  frog. 

The  eggs  of  this  frog  are  laid  in  shallow  water  in  the  early 
spring.  Masses  of  several  hundred,  which  may  be  found  at- 
tached to  twigs  or  other  supports  under  water,  are  deposited  at 
a  single  laying.  Immediately  before  leaving  the  body  of  the 
female  they  receive  a  coating  of  jelly  like  material,  which  swells 
up  after  the  eggs  are  laid.  Thus  they  are  protected  from  the 
attack  of  fish  or  other  animals  which  might  use  them  as  food. 
The  upper  side  of  the  egg  is  dark,  the  light-colored  side  being 
weighted  down  with  a  supply  of  yolk  (food).  The  fertilized  egg 
soon  segments  (divides  into  many  cells),  and  in  a  few  days,  if  the 
weather  is  warm,  these  eggs  have  each  grown  into  an  oblong  body 
which  shows  the  form  of  a  tadpole.  Shortly  after  the  tadpole 
wriggles  out  of  the  jellylike  case  and  begins  life  outside  the  egg.  At 
first  it  remains  attached  to  some  water  weed  by  means  of  a  pair 
of  suckerlike  projections;  later  a  mouth  is  formed,  and  the  tad- 
pole begins  to  feed  upon  algae  or  other  tiny  water  plants.  At 
this  time,  about  two  weeks  after  the  eggs  were  laid,  gills  are 


5 


if  w       Mr  -  '     .■'■^- 


**-  ¥" 


Development  of  a  frog.  1,  two  cell  stage  ;  2,  four  cell  stage ;  3,  8  cells  are  formed, 
notice  the  upper  cells  are  smaller ;  in  (4)  the  lower  cells  are  seen  to  be  much 
,  larger  because  of  the  yolk  ;  5,  the  egg  has  continued  to  divide  and  has  formed 
a  gastrula;  C,  7,  the  body  is  lengthening,  head  is  seen  at  the  right  hand  end; 
8,  the  young  tadpole  with  external  gills;  9,  10,  the  gills  are  internal,  liitid  legs 
beginning  to  form;  11,  the  hind  legs  show  plainly;  12,  i:j.  14,  la^or  stages  in 
development;  15,  the  adult  frog.  Figures  1,  2,  .S.  4.  .'>,  (\,  and  7  are  very 
much  enlarged.     (Drawn  after  Leukart  and  Kny  by  Frank  M.  Wheat.) 

245 


246 


A  STUDY   OF   VERTEBRATES 


present  on  the  outside  of  the  body.  Soon  after,  the  external  gills 
are  replaced  by  gills  which  grow  out  under  a  fold  of  the  skin  which 
forms  an  operculum  somewhat  as  in  the  fish.  Water  reaches  the 
gills  through  the  mouth  and  passes  out  through  a  hole  on  the  left 
side  of  the  body.  As  the  tadpole  grows  larger,  legs  appear,  the 
hind  legs  first,  although  for  a  time  locomotion  is  performed  by 
means  of  the  tail.  In  the  leopard  frog  the  change  from  the  egg 
to  adult  is  completed  in  one  summer.  In  late  July  or  early  August, 
the  tadpole  begins  to  eat  less,  the  tail  becomes  smaller  (being 
absorbed  into  other  parts  of  the  body),  and  before  long  the  trans- 
formation from  the  tadpole  to  the  young  frog  is  complete.  In 
the  green  frog  and  bullfrog  the  metamorphosis  is  not  completed 
until  the  beginning  of  the  second  summer.  The  large  tadpoles 
of  such  forms  bury  themselves  in  the  soft  mud  of  the  pond  bottom 
during  the  winter. 

Shortly  after  the  legs  appear,  the  gills  begin  to  be  absorbed,  and 
lungs  take  their  place.  At  this  time  the  young  animal  may  be 
seen  coming  to  the  surface  of  the  water  for  air.  Changes  in  the 
diet  of  the  animal  also  occur ;  the  long,  coiled  intestine  is  trans- 
formed into  a  much  shorter  one.  The  animal,  now  insectivorous 
in  its  diet,  becomes  provided  with  tiny  teeth  and  a  mobile  tongue, 

instead  of  keeping  the 
horny  jaws  used  in 
scraping  off  algae.  After 
the  tail  has  been  com- 
pletely absorbed  and 
the  legs  have  become 
full  grown,  there  is 
no  further  structural 
change,  and  the  meta- 
morphosis is  complete. 
Development  of 
Birds.  —  The  white  of 
the  hen's  egg  is  put  on 

At  tli«^  left  is  ahfii's  c^k,  opened  to  show  the  embryo  during  the  paSSage  of 
at  the  center  (tlie  spot  surrounded  by  a  hghter  ^^e  real  egg  (which  is 
area).     At  the  right  is  an  Ji.nghsh  sparrow  one     .  "^    ^ 

day  after  hatching.  in  the  yoke  or  yellow 


W^M 

fi 

^^--^ 

v'^fl 

1   J 

BHK^-'    m 

V    '^^^i 

^5 

^^^^       "^^^^K^^^M 

THE   BIRD 


247 


portion)  to  the  outside  of  the  body.  Before  the  egg  is  laid  a  shell 
is  secreted  over  its  surface.  If  the  fertilized  egg  of  a  hen  be 
broken  and  carefully  examined,  on  the  surface  of  the  yolk  will  be 
found  a  little  circular  disk.  This  is  the  beginning  of  the  growth  of 
an  embryo  chick.  If  a  series  of  eggs  taken  from  an  incubator 
at  periods  of  twenty-four  hours  or  less  apart  were  examined,  this 
spot  would  be  found  at  first  to  increase  in  size ;  later  the  little 
embryo  would  be  found  lying  on  the  surface.  Still  later  small 
blood  vessels  could  be  made  out  reaching  into  the  yolk  for  food, 
the  tiny  heart  beating  as  early  as  the  second  day  of  incubation. 
After  about  three  weeks  of  incubation  the  little  chick  hatches ; 
that  is,  breaks  the  shell,  and  emerges  in  almost  the  same  form  as 
the  adult. 

Development  of  a  Mammal.  —  In  mammals  after  fertilization 
the  egg  undergoes  development  within  the  body  of  the  mother. 
Instead    of    blood    vessels 


connecting  the  embryo  with 
the  yolk  as  in  the  chick, 
here  the  blood  vessels  are 
attached  to  an  absorbing 
organ,  known  as  the  pla- 
centa. This  structure  sends 
branch  like  processes  into 
the  wall  of  the  uterus  (the 
organ  which  holds  the  em- 
bryo) and  absorbs  nour- 
ishment and  oxygen  by 
osmosis  from  the  blood 
of  the  mother.  After  a 
length  of  time  which  varies 

in  different  species  of  mam-     The  embryo  (e)  of  a  rabbit,  showing  the  ab- 
TYiflk      rfrom      flbniit     thrpp  sorbing   organ;    the    branch-Uke  processes 

mais    {nom    aoouL    tnree        ^^.^^^    ^,^^^^j^    ,^j^^^   ^^^^^^^   ^^^  mother 

weeks   in    a    guinea    pig    to  being  shown  at  (v)  -,    ct,  the  tul>e  connect- 

twenty-two  months  in  an        "^  f^t^^ll^^^lfu-' Hareke,'.;'''''"  ""'"' 
elephant),  the  young  ani- 
mal  leaves   the    protecting    body   of    the   mother,    or    is    ])orn. 
The  young,  usually,  are  born  in  a  helpless  condition,  then  nour- 


248  A  STUDY  OF  VERTEBRATES 

ished  by  milk  furnished  by  the  mother  until  they  are  able  to  take 
other  food.  Thus  we  see  as  we  go  higher  in  the  scale  of  life  fewer 
eggs  formed,  but  those  few  eggs  are  more  carefully  protected  and 
cared  for  by  the  parents.  The  chances  of  their  growth  into  adults 
are  much  greater  than  in  the  cases  when  many  eggs  are  produced. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Bigelow,  Introduction  to  Biology.     The  Macmillan  Company. 

Cornell  Nature  Study  Leaflets.     Bulletins  XVI,  XVII. 

Davison,  Practical  Zoology,  pages  185-199.     American  Book  Company. 

Hodge,  Nature  Study  and  Life,  Chaps.  XVI,  XVII.     Ginn  and  Company. 

Sharpe,  Laboratory  Manual,  pp.  195,  204-209.    American  Book  Company. 

ADVANCED 

Dickerson,  The  Frog  Book.     Doubleday,  Page  and  Company. 
Holmes,  The  Biology  of  the  Frog.     The  Macmillan  Company. 
Jordan,  Fishes.     Henry  Holt  and  Company. 

Morgan,  The  Development  of  the  Frog's  Egg.     The  Macmillan  Company. 
Needham,  General  Biology.    Comstock  Publishing  Company. 


XVII.     HEREDITY,  VARIATION,  PLANT  AND  ANIMAL 

BREEDING 

Problems,  —  To  determine  what  makes  the  offspring  of  ani- 
inals  or  plants  tend  to  be  like  their  parents. 

To  determine  what  makes  the  offspring  of  animals  and 
plants  differ  from  their  parents. 

To  learn  about  some  methods  of  plant  and  animal  breeding. 

{a)  By  selection. 

ib)   By  hybridizing. 

(c)    By  other  T)%ethods. 

To  learn  about  some  methods  of  improving  the  human  race. 

{a)    By  eugenics. 

ib)    By  euthenics. 

Suggestions  for  Laboratory  Work 

Laboratory  exercise.  — •  On  variation  and  heredity  among  members  of  a 
class  in  the  schoob^oom. 

Laboratory  exercise. —  On  construction  of  curve  of  variation  in  measure- 
ments from  given  plants  or  animals. 

Laboratory  demonstration.  —  Stained  Qgg  eel's  (ascaris)  to  show  chromo- 
somes. 

Laboratory  demonstrations. —  To  illustrate  the  part  played  in  plant  or 
animal  breeding  by 

(a)  selection. 

(6)  hybridizing. 

(c)  budding  and  grafting. 

Laboratory  demonstration.  —  From  charts  to  illustrate  how  human  char- 
acteristics may  be  inherited. 

HEREDITY  AND   EUGENICS 

Heredity  and  what  it  Means.  —  As  I  look  over  the  faces  of  the 
boys  in  my  class  I  notice  that  each  boy  seems  to  be  more  or  less 
like  each  other  boy  in  the  class;  he  has  a  head,  body,  arms,  and 
legs,  and  even  in  minor  ways  he  resembles  each  of  the  other  boys 
in  the  room.     Moreover,  if  I  should  ask  him  I  have  no  doubt 

249 


250 


HEREDITY  AND   VARIATION 


but  that  he  would  tell  me  that  he  resembled  in  many  respects  his 
mother  or  father.  Likewise  if  I  should  ask  his  parents  whom  he 
resembled,  they  would  say,  "  I  can  see  his  grandmother  or  his 
grandfather  in  him." 

This  wonderful  force  which  causes  the  likeness  of  the  child  to 
its  parents  and  to  their  parents  we  call  heredity.  Heredity  causes 
the  plants  as  well  as  animals  to  be  like  their  parents.  If  we 
trace  the  workings  of  heredity  in  our  own  individual  case,  we  will 
probably  find  that  we  are  molded  like  our  ancestors  not  only  in 
physical  characteristics  but  in  mental  qualities  as  well.  The 
ability  to  play  the  piano  or  to  paint  is  probably  as  much  a  case  of 
inheritance  as  the  color  of  our  eyes  or  the  shape  of  our  nose.  We 
are  a  complex  of  physical  and  mental  characters,  received  in  part 
from  all  our  ancestors. 

Variation.  —  But  I  notice  another  thing ;  no  boy  in  the  class 
before  me  is  exactly  like  any  other  boy,  even  twins  having  minute 
differences.     In  this  wonderful  mold  of  nature  each  one   of  us 


ifl 


Variations  in  the  Cataipa  caterpillar.     (Photographed,  natural  ^ize, 

by  Davison.) 


HEREDITY  AND   VARIATION  251 

tends  to  be  slightly  different  from  his  or  her  parents.  Each  plant, 
each  animal,  varies  to  a  greater  or  lesser  degree  from  its  immediate 
ancestors  and  may  vary  to  a  very  great  degree.  This  factor  in 
the  lives  of  plants  and  animals  is  called  variation.  Heredity  and 
variation  are  the  cornerstones  on  which  all  the  work  in  the  improve- 
ment of  plants  and  animals,  including  man  himself,  is  built. 

The  Bearers  of  Heredity.  —  We  have  seen  that  somewhere  in 
every  living  cell  is  a  structure  known  as  a  nucleus.  In  this  nucleus, 
which  is  a  part  of  the  living  matter  of  the  cell,  are  certain  very 
minute  structures  always  present,  known  as  chromosomes.  These 
chromosomes  (so  called  because  they  take  up  color  when  stained) 
are  believed  to  be  the  structures  which  contain  the  determiners 
of  the  qualities  which  may  be  passed  from  parent  plant  to  offspring 
or  from  animal  to  animal ;  in  other  words,  the  qualities  that  are 
inheritable  (see  page  252). 

The  Germ  Cells.  —  But  it  has  been  found  that  certain  cells  of 
the  body,  the  egg  and  the  sperm  cells,  before  uniting  contain  only 
half  as  many  chromosomes  as  do  the  body  cells.  In  preparing 
for  the  process  of  fertilization,  half  of  these  elements  have  been 
eliminated,  so  that  when  the  egg  and  sperm  cell  are  united  they 
will  have  the  full  number  of  chromosomes  that  the  other  cells 
have. 

If  the  chromosomes  carry  the  determiners  of  the  characters 
which  are  inheritable,  then  it  is  easy  to  see  that  a  fertilized  egg  must 
contain  an  equal  number  of  chromosomes  from  the  bodies  of  each 
parent.  Consequently  characteristics  from  each  parent  are 
handed  down  to  the  new  individual.  This  seems  to  be  the  way  in 
which  nature  succeeds  in  obtaining  variation,  by  providing  cell 
material  from  two  different  individuals. 

Offspring  are  Part  of  their  Ancestors.  —  We-  can  see  that  if 
you  or  I  receive  characteristics  from  our  parents  and  they  received 
characteristics  from  their  parents,  then  we  too  must  have  some  of 
the  characteristics  of  the  grandparents,  and  it  is  a  matter  of  com- 
mon knowledge  that  each  of  us  does  have  some  trait  or  lineament 
which  can  be  traced  back  to  our  grandfather  or  grandmotlier. 
Indeed,  as  far  back  as  we  are  able  to  go,  ancestors  have  added 
something. 


252 


HEREDITY  AND   VARIATION 


sp.n. 
-  cent. 


--•/ — e.n 


COMPARISON 

OF 

SEXUAL  AND  ASEXUAL 
CELL  "REPROLUCTION 


HEREDITY   AND  VARIATION 


253 


Charles  Darwin  and  Natural  Selection.  —  The  grciit  English- 
man Charles  Darwin  was  one  of  the  first  scicuitists  to  realize  how 
this  great  force  of  heredity  applied  to  the  development  or  (evolu- 
tion of  plants  and  animals.  He  knew  that  although  animals 
and  plants  were  like  their  ancestors,  they  also  tended  to  vary. 
In  nature,  the  variations  which  best  fitted  a  plant  or  animal  for 
life  in  its  own  environment  were  the  ones  which  were  handed 
down  because  those  having  variations  which  were  not  fitted  for 
life  in  that  particular  environment  would  die.  Thus  nature 
seized  upon  favorable  variations  and  after  a  time,  as  the  descend- 
ants of  each  of  these  individuals  also  tended  to  vary,  a  new  species 
of  plant  or  animal,  fitted  for  the  place  it  had  to  live  in,  would  be 
gradually  evolved. 

Mutations.  —  Recently  a  new  method  of  variation  has  been 
discovered  by  a  Dutch  naturalist,  named  Hugo  de  Vries.  He 
found  that  new  species  of  plants  and  animals  arise  suddenly  by 
'*  mutations  "  or  steps.  This  means  that  new  species  instead  of 
arising  from  very  slight  variations,  continuing  during  long  periods 
of  years  (as  Darwin  believed) ,  might  arise  very  suddenly  as  a  very 
great  variation  which  would  at  once  breed  true.  It  is  easily  seen 
that  such  a  condition  would  be  of  immense  value  to  breeders,  as 
new  plants  or  animals  quite  unlike  their  parents  might  thus  be 
formed  and  perpetuated.  It  will  be  one  of  the  future  problems 
of  plant  and  animal  breeders  to  isolate  and  breed  "  mutants," 
as  such  organisms  are 
called. 

Artificial  Selection. — 
Darwin  reasoned  that 
if  nature  seized  upon 
favorable  variants,  then 
man,  by  selecting  the 
variations  he  wanted, 
could  form  new  varie- 
ties of  plants  or  ani- 
mals much  more  quickly 

than    nature.        And     so      improvement  in  corn  by  selection       To  the  left    the 

corn    improved    by  selection  from  the  origiiuil 

to-day  plant  or  animal         type  at  the  right. 


254  HEREDITY   AND  VARIATION 

breeders  select  the  forms  having  the  characters  they  wish  to  per- 
petuate and  breed  them  together.  This  method  used  by  plant 
and  animal  breeders  is  known  as  selection. 

Selective  Planting.  —  By  selective  planting  we  mean  choosing 
the  best  plants  and  planting  the  seed  from  these  plants  with  a  view  of 
improving  the  yield.  In  doing  this  we  must  not  necessarily  select 
the  most  perfect  fruits  or  grains,  but  must  select  seeds  from  the 
test  plants.  A  wheat  plant  should  be  selected  not  from  its  yield 
alone,  but  from  its  ability  to  stand  disease  and  other  unfavorable 
conditions.  In  1862  a  Mr.  Fultz,  of  Pennsylvania,  found  three 
heads  of  beardless  or  bald  wheat  while  passing  through  a  large 
field  of  bearded  wheat.  These  were  probably  mutants  which  had 
lost  the  chaff  surrounding  the  kernel.  Mr.  Fultz  picked  them  out, 
sowed. them  by  themselves,  and  produced  a  quantity  of  wheat  now 
known  favorably  all  over  the  world  as  the  Fultz  wheat.  In  select- 
ing wheat,  for  example,  we  might  breed  for  a  number  of  different 
characters,  such  as  more  starch,  or  more  protein  in  the  grain,  a 
larger  yield  per  acre,  ability  to  stand  cold  or  drought  or  to  resist 
plant  disease.  Each  of  these  characters  would  have  to  be  sought 
for  separately  and  could  only  be  obtained  after  long  and  careful 
breeding.  The  work  of  Mendel  (see  page  257)  when  applied  to 
plant  breeding  will  greatly  shorten  the  time  required  to  produce 
better  plants  of  a  given  kind.  By  careful  seed  selection,  some 
Western  farmers  have  increased  their  wheat  production  by  25 
per  cent.  This,  if  kept  up  all  over  the  United  States,  would  mean 
over  $100,000,000  a  year  in  the  pockets  of  the  farmers. 

Hybridizing.  —  We  have  already  seen  that  pollen  from  one 
flower  may  be  carried  to  another  of  the  same  species,  thus  produc- 
ing seeds.  If  pollen  from  one  plant  be  placed  on  the  pistil  of  an- 
other of  an  allied  species  or  variety,  fertilization  may  take  place 
and  new  plants  be  eventually  produced  from  the  seeds.  This 
process  is  known  as  hybridizing,  and  the  plants  produced  by  this 
process  known  as  hybrids. 

Hybrids  are  extremely  variable,  rarely  breed  from  seeds,  and  often 
are  apparently  quite  unlike  either  parent  plant.  They  must  be 
grown  for  several  years,  and  all  plants  that  do  not  resemble  the 
desired  variety  must  be  killed  off,  if  we  expect  to  produce  a  hybrid 


HEREDITY  AND   VARIATION 


255 


that  will  breed  more  plants  like  itself.  LiitluT  Burbaiik,  the 
great  hybridizer  of  California,  destroys  tens  of  thousands  of  plants 
in  order  to  get  one  or  two  with  the  charac- 
ters which  he  wishes  to  preserve.  Thus  he 
is  yearly  adding  to  the  wealth  of  this 
country  by  producing  new  plants  or  fruits 
of  commercial  value.  A  number  of  years 
ago  he  succeeded  in  growing  a  new  va- 
riety of  potato,  which  has  already  en- 
riched the  farmers  of  this  countrj^  about 
$20,000,000.  One  of  his  varieties  of  black 
walnut  trees,  a  very  valuable  hard  wood, 
grows  ten  to  twelve  times  as  rapidly  as 
ordinary  black  walnuts.  With  lumber 
yearly  increasing  in  price,  a  quick  grow- 
ing tree  becomes  a  very  valuable  com- 
mercial product.  Among  his  famous 
hybrids  are  the  plumcot,  a  cross  between 
an  apricot  and  a  plum,  his  numerous  va- 
rieties of  berries  and  his  splendid  '^  Climax" 
plum,  the  result  of  a  cross  between  a 
bitter  Chinese  plum  and  an  edible  Jap- 
anese plum.  But  none  of  Burbank's 
products  grow  from  seeds ;  they  are  all  produced  asexually,  from 
hybrids  by  some  of  the  processes  described  in  the  next  paragraph. 

The  Department  of  Agriculture  and  its  Methods.  — ■  The  Depart- 
ment of  Agriculture  is  also  doing  splendid  work  in  producing  new 
varieties  of  oranges  and  lemons,  of  grain  and  various  garden  vege- 
tables. The  greatest  possibilities  have  been  shown  by  department 
workers  to  be  open  to  the  farmer  or  fruit  grower  through  hybrid- 
izing, and  by  budding,  grafting,  or  slipping. 

Budding.  —  If  a  given  tree,  for  example,  produces  a  kind  of  fruit 
which  is  of  excellent  quality,  it  is  possible  sometimes  to  attach  parts 
of  the  tree  to  another  strong  tree  of  the  same  species  that  may  not 
bear  good  fruit.  This  is  done  by  budding.  A  T-shaped  incision 
is  cut  in  the  bark  ;  a  bud  from  the  tree  bearing  the  desired  fruit  is 
placed  in  the  cut  and  bound  in  place.     When  a  shoot  from  the 


In  hybridizing,  all  of  the 
flower  is  removed  at  the 
line  (W)  except  the  pis- 
til (P).  Then  pollen 
from  another  flo\v(>r  of  a 
nearly  related  kind  is 
placed  on  the  pistil  and 
the  pollinated  flower 
covered  up  with  a  paper 
bag.  Can  you  explain 
why? 


256 


HEREDITY  AND   VARIATION 


eml)('(l(locl  1)11(1  grows  out  the  following  spring,  it  is  found  to  have 
all  the  characters  of  the  tree  from  which  it  was  taken. 


! 


Steps  in  budding,  a,  twig  having  suitable  buds  to  use;  b,  method  of  cutting 
out  bud ;  c,  how  the  bark  is  cut ;  d,  how  the  bark  is  opened ;  e,  inserting 
the  bud ;  /,  the  bud  in  place ;  g,  the  bud  properly  bound  in  place. 

Grafting.  —  Of  much  the  same  nature  is  grafting.     Here,  how- 
ever, a  small  portion  of  the  stem  of  the  closely  allied  tree  is  fas- 


VI 


f 


I 


tened  into  the  trunk  of  the  growing  tree 
in  such  a  manner  that  the  two  cut  layers 
just  under  the  bark  will  coincide.  This 
will  allow  of  the  passage  of  food  into 
the  grafted  part  and  insure  the  ultimate 
growth  of  the  twig.  Grafting  and  bud- 
ding are  of  considerable  economic  value 
to  the  fruit  grower,  as  it  enables  him 
Steps  in  tongue  grafting,  a,  the  to  producc  at  will,  trees  bearing  choice 

two  branches  to  be  formed  ; 
b,  a  tongue  cut  in  each  ;  c,  fit- 
ted  together ;  d,   method   of 

wrappmg.  plant  propagation  are  by  means  of  run- 

ners, as  when  strawberry  plants  strike  root  from  long  stems  that 
run  along  the  gJOund ;  layering,  where  roots  may  develop  on 
covered  up  branches  of  blackberry  or  raspberry  plants  ;  slips,  roots 
developing  from  stems  which  are  cut  off  and  placed  in  moist 
sand ;  from  tubers,  as  in  planting  potatoes ;    and  by  means  of 

^  For  full  directions  for  budding  and  grafting,  see  Goff  and  Mayne,  First  Princi- 
ples of  Agriculture,  Chap.  XIX,  Mayne  and  Hatch,  High  School  Agriculture, 
pp.  159-165,  or  Hodge,  Nature  Study  and  Life,  pages  169-17&. 


varieties  of  fruit. ^ 

Other  Methods.  —  Other  methods  of 


HEREDITY  AND   VARIATION 


257 


bulbs,  as  the  tulip  or  hyacinth.  All  of  the  above  means  of  prop- 
agation are  asexual  and  are  of  importance  in  our  problem  of 
plant  breeding. 


Plant  breeding  plots.     (Minnesota  Experiment  Station.) 


The  Work  of  Gregor  Mendel.  —  Fifty  years  ago,  an  Austrian 
monk,  Gregor  Mendel,  found  in  breeding  garden  peas  that  these 
plants  passed  on  certain  fixed  characters^  as  the  shape  of  the 
seed,  the  color  of  the  pod  when  ripe,  and  others,  and  that  when 
two  pea  plants  of  different  characters  were  crossed,    one  of  these 

PUNTER,    CIV.    BI. 17 


258 


HEREDITY  AND   VARIATION 


9jQ 


A: 


/. 


Q 


\ 


OO 


characters  would  be  likely  to  appear  in  the  offspring  of  the 
second  generation  in  the  ratio  of  three  to  one.  Such  characters 
as  would  appear  to  the  exclusion  of  others  in  the  first  crossing  of 

the  plants  were  called  dominanty 
the  ones  not  appearing,  reces- 
sive characteristics.  When  these 
seeds  were  again  sown  the  ones 
bearing  a  recessive  characteris- 
tic would  produce  only  peas 
with  this  recessive  characteris- 
tic, but  the  ones  with  a  domi- 
nant characteristic  might  give 
rise  to  a  pure  dominant  or  to 
offspring  having  partly  a  domi- 
nant and  partly  a  recess've 
character ;  pure  dominants  be- 
ing to  the  mixed  offspring  in  the 
ratio  of  1  to  2.  The  pure  domi- 
nants if  bred  with  others  like 
themselves  would  produce  only 
pure  dominants,  but  the  cross 
breeds  would  again  produce 
mixed  offspring  of  three  kinds 
in  the  ratio  of  one  dominant 
to  two  cross  breeds  and  one 
recessive.  The  feature  of  this  work  that  interests  us  is  that  unit 
characters  are  passed  along  by  heredity  in  the  germ  cells  pure, 
that  is,  unchanged,  from  one  generation  to  another,  and  inde- 
pendently of  each  other. 

Determiners  of  Character.  —  A  child  then  resembles  his  par- 
ents in  some  definite  particulars  because  certain  determiners  of 
characters  have  been  present  in  the  germ  cells  of  one  of  the 
parents.  If  the  determiner  of  a  certain  character  is  absent 
from  the  germ  cells  of  both  parents,  it  will  be  absent  in  all  of 
their  offspring. 

These  discoveries  of  Mendel  are  of  the  greatest  importance  in 
plant  and  animal  breeding  because  they  enable  the  breeder  to 


Illustration  of  Mendel's  Law. 


HEREDITY  AND   VARIATION 


259 


isolate  certain  characters  and  by  proper  selection  to  breed  varieties 
which  have  these  desired  characters,  instead  of  waiting  for  a  chance 
union  of  the  desired  characters  by  nature. 

Animal  Breeding.  —  It  has  been  pointed  out  that  the  domesti- 
cation of  wild  animals,  the  horse,  cattle,  sheep,  goats,  and  the  dog, 
marked  a  great  advance  in  civilization  in  the  history  of  the  earth's 
peoples.  As  the  young  of 
these  animals  came  to  be 
bred  in  captivity  the  peo- 
ples owning  them  would 
undoubtedly  pick  out  the 
strongest  and  best  of 
the  offspring,  killing  off 
the  others  for  food.  Thus 
they  came  unconsciously 
to  select  and  aid  nature 
in  producing  a  stronger 
and  better  stock.  Later 
man  began  to  recognize 
certain  characters  that  he 
wished  to  have  in  horses, 
dogs,  or  cattle,  and  so  by 
slow  processes  of  breeding 
and  "  crossing "  or  hy- 
bridizing one  nearly  allied 
form  with  another  the 
numerous  groups  of  do- 
mesticated animals  began 
to  appear. 

In  Darwin's  time    ani- 
mal  breeding  was  so  far 
advanced  that  he  got  his 
ideas  of  selection  by  na- 
ture in  evolution  from  the  artificial  selection  practiced  by  animal 
breeders.     A  glance  at  the  pictures  will  give  some  idea  of  the 
changes  that  have   taken    place   in   the    form  of  some  animals 
since  man  began  to  breed  them  a  few  thousand  years  ago. 


What  has  resulted  from  artificial  selection 
among  dogs.     (After  Romanes.) 


260 


HEREDITY  AND   VARIATION 


Some  Domesticated  Animals.  —  Our  domesticated  dogs  are 
descended  from  a  number  of  wolflike  forms  in  various  parts  of  the 
world.  All  the  present  races  of  cats,  on  the  other  hand,  seem  to 
be  traced  back  to  Egypt.  Modern  horses  are  first  noted  in 
Europe  and  Asia,  but  far  older  forms  flourished  on  the  earth  in 
former  geologic  periods.  It  is  interesting  to  note  that  America 
was  the  original  home  of  the  horse,  although  at  the  time  of  the 

earliest  explorers  the  horse 
was  unknown  here,  the 
wild  horse  of  the  Western 
plains  having  arisen  from 
horses  introduced  by  the 
Spaniards.  Long  ages  ago, 
the  first  ancestors  of  the 
horse  were  probably  little 
^,     ,  ,  .       r  X,  X  .  animals  about  the  size  of 

The   four-toed    ancestor    of    the   present    horse,  t          t 

restored  from  a  study  of  its  fossil  skeleton,  a  foX.      The  earliest  horse 

(After  Knight  in  American  Museum  of  Nat-  ^^  have  knowledge  of  had 

ural  History.)  r          ^                  ^^       r                i 

tour  toes  on  the  tore  and 
three  toes  on  the  hind  foot.  Thousands  of  years  later  we  find  a 
larger  horse,  the  size  of  a  sheep,  with  a  three-toed  foot.  By 
gradual  changes,  caused  by  the  tendency  of  the  animals  to  vary 
and  by  the  action  of  the  surroundings  upon  the  animal  in  preserv- 
ing these  variations,  there  was  eventually  produced  our  present 
horse,  an  animal  with  legs  adapted  for  rapid  locomotion,  with 
feet  particularly  fitted  for  the  life  in  open  fields,  and  with  teeth 
which  serve  well  to  seize  and  grind  herbage.  Knowledge  of  this 
sort  was  also  used  by  Darwin  to  show  that  constant  changes  in 
the  form  of  animals  have  been  taking  place  since  life  began  on 
the  earth. 

The  horse,  which  for  some  reason  disappeared  in  this  country, 
continued  to  exist  in  Europe,  and  man,  emerging  from  his  early 
savage  condition,  began  to  make  use  of  the  animal.  We  know  the 
horse  was  domesticated  in  early  Biblical  times,  and  that  he  soon 
became  one  of  man's  most  valued  servants.  In  more  recent 
times,  man  has  begun  to  change  the  horse  by  breeding  for  certain 
desired  characteristics.     In  this  manner  have  been  established  and 


HEREDITY   AND   VARIATION  2G1 

improved  the  various  types  of  horses  famihar  to  us  as  draft  horses, 
coach  horses,  hackneys,  and  the  trotters. 

It  is  needless  to  say  that  all  the  various  domesticated  animals 
have  been  tremendously  changed  in  a  similar  manner  sinc(;  civilized 
man  has  come  to  live  on  the  earth.  When  we  realize  the  very 
great  amount  of  money  invested  in  domesticated  animals ;  that 
there  are  over  60,000,000  each  of  sheep,  cattle,  and  swine  and 
over  20,000,000  horses  owned  in  this  country,  then  we  may  see 
how  very  important  a  part  the  domestic  animals  play  in  our  lives. 

Improvement  of  Man.  —  If  the  stock  of  domesticated  animals 
can  be  improved,  it  is  not  unfair  to  ask  if  the  health  and  vigor 
of  the  future  generations  of  men  and  women  on  the  earth  might 
not  be  improved  by  applying  to  them  the  laws  of  selection.  This 
improvement  of  the  future  race  has  a  number  of  factors  in  which 
we  as  individuals  may  play  a  part.  These  are  personal  hygiene, 
selection  of  healthy  mates,  and  the  betterment  of  the  environment. 

Personal  Hygiene.  —  In  the  first  place,  good  health  is  the  one 
greatest  asset  in  life.  We  may  be  born  with  a  poor  bodily  machine, 
but  if  we  learn  to  recognize  its  defects  and  care  for  it  properly, 
we  may  make  it  do  its  required  work  effectively.  If  certain  muscles 
are  poorly  developed,  then  by  proper  exercise  we  may  make  them 
stronger.  If  our  eyes  have  some  defect,  we  can  have  it  remedied 
by  wearing  glasses.  If  certain  drugs  or  alcohol  lower  the  efficiency 
of  the  machine,  we  can  avoid  their  use.  With  proper  care  a  poorly 
developed  body  may  be  improved  and  do  effective  work. 

Eugenics.  —  When  people  marry  there  are  certain  things  that 
the  individual  as  well  as  the  race  should  demand.  The  most 
important  of  these  is  freedom  from  germ  diseases  which  might  be 
handed  down  to  the  offspring.  Tuberculosis,  that  dread  white 
plague  which  is  still  responsible  for  almost  one  seventh  of  all 
deaths,  epilepsy,  and  feeble-mindedness  are  handicaps  which  it 
is  not  only  unfair  but  criminal  to  hand  down  to  posterity.  The 
science  of  being  well  born  is  called  eugenics. 

The  Jukes.  —  Studies  have  been  made  on  a  number  of  ditferent 
families  in  this  country,  in  which  mental  and  moral  defects  were 
present  in  one  or  both  of  the  original  parents.  The  ''Jukes  " 
family  is  a  notorious  example.     The  first  mother  is  Icnown  as 


202 


HEREDITY   AND   VARIATION 


"  Margaret,  the  mother  of  criminals."  In  seventy-five  years  the 
progenj^  of  the  original  generation  has  cost  the  state  of  New  York 
over  a  million   and   a   quarter  of  dollars,   besides  giving  over 


A* 

X 


K 


©H®ET®~iT© 


N 


®® 


N 


li 


hhSW^ 


N 

In  this  and  the  following  diagrams  the  circle  represents  a  female,  the  square  a 
male,  (n)  means  normal ;  Q  means  feeble-minded  ;  A,  alcoholic ;  T,  tuber- 
cular. This  chart  shows  the  record  of  a  certain  family  for  three  generations. 
A  normal  woman  married  an  alcoholic  and  tubercular  man.  He  must  have 
been  feeble-minded  also,  as  two  of  his  children  were  born  feeble-minded.  One 
of  these  children  married  another  feeble-minded  woman,  and  of  their  five 
children  two  died  in  infancy  and  three  were  feeble-minded.  (After  Daven- 
port.) 

to  the  care  of  prisons  and  asylums  considerably  over  a  hun- 
dred feeble-minded,  alcoholic,  immoral,  or  criminal  persons. 
Another  case  recently  studied  is  the  "  Kallikak  "  family.^  This 
family  has  been  traced  to  the  union  of  Martin  Kallikak,  a  young 
soldier  of  the  War  of  the  Revolution,  with  a  feeble-minded  girl. 


I^^^^T<^ 


N 


d.       C.  d. 


m 

d.  d.  d.  I 
l-nj.ln/.lnj.l 


This  chart  shows  that  feeble-mindedness  is  a  characteristic  sure  to  be  handed 
down  in  a  family  where  it  exists.  The  feeble-minded  woman  at  the  top  left 
of  the  chart  married  twice.  The  first  children  from  a  normal  father  are  all 
normal,  but  the  other  children  from  an  alcoholic  father  are  all  feeble-minded. 
The  right-hand  side  of  the  chart  shows  a  terrible  record  of  feeble-mindedness. 
Should  feeble-minded  people  be  allowed  to  marry?     (After  Davenport.) 

^The  name  Kallikak  is  fictitious. 


HEREDITY   AND    VARIATION  263 

She  had  a  feeble-minded  son  from  whom  there  have  been  to  the 
present  time  480  descendants.  Of  these  33  were  sexually  immoral, 
24  confirmed  drunkards,  3  epileptics,  and  143  feeble-minded.  The 
man  who  started  this  terrible  line  of  immorality  and  feeble-minded- 
ness  later  married  a  normal  Quaker  girl.  From  this  couple  a  line 
of  496  descendants  have  come,  with  no  cases  of  feeble-mindedness. 
The  evidence  and  the  moral  speak  for  themselves  ! 

Parasitism  and  its  Cost  to  Society.  —  Hundreds  of  families 
such  as  those  described  above  exist  to-day,  spreading  disease, 
immorality,  and  crime  to  all  parts  of  this  countr^^  The  cost  to 
society  of  such  families  is  very  severe.  Just  as  certain  animals 
or  plants  become  parasitic  on  other  plants  or  animals,  these  families 
have  become  parasitic  on  society.  They  not  only  do  harm  to  others 
by  corrupting,  stealing,  or  spreading  disease,  but  they  are  actually 
protected  and  cared  for  by  the  state  out  of  pul)lic  money.  Largely 
for  them  the  poorhouse  and  the  asylum  exist.  They  take  from 
society,  but  they  give  nothing  in  return.     They  are  true  parasites. 

The  Remedy.  —  If  such  people  were  lower  animals,  we  would 
probably  kill  them  off  to  prevent  them  from  spreading.  Humanity 
will  not  allow  this,  but  we  do  have  the  remedy  of  separating  the 
sexes  in  asylums  or  other  places  and  in  various  ways  preventing 
intermarriage  and  the  possibilities  of  perpetuating  such  a  low  and 
degenerate  race.  Remedies  of  this  sort  have  been  tried  success- 
fully in  Europe  and  are  now  meeting  with  success  in  this  country. 

Blood  Tells.  —  Eugenics  show  us,  on  the  other  hand,  in  a  study 
of  the  families  in  which  are  brilliant  men  and  women,  the  fact  that 
the  descendants  have  received  the  good  inheritance  from  their 
ancestors.  The  following,  taken  from  Davenport's  Heredity  in 
Relation  to  Eugenics,  illustrates  how  one  family  has  been  famous 
in  American  History. 

In  1667  Elizabeth  Tuttle,  ''  of  strong  will,  and  of  extreme 
intellectual  vigor,  married  Richard  Edwards  of  Hartford,  Conn., 
a  man  of  high  repute  and  great  erudition.  From  their  one  son 
descended  another  son,  Jonathan  Edwards,  a  noted  divine,  and 
president  of  Princeton  College.  Of  the  descendants  of  Jonathan 
Edwards  much  has  been  written ;  a  brief  catalogue  must  suffice  : 
Jonathan  Edwards,  Jr.,  president  of  Union  College;    Timothy 


N 


264  HEREDITY  AND   VARIATION 

D wight,  president  of  Yale ;  Sereno  Edwards  D wight,  president  of 
Hamilton  College ;  Theodore  Dwight  Woolsey,  for  twenty-five 
years  president  of  Yale  College ;    Sarah,  wife  of  Tapping  Reeve, 

\Sh0  BtO 

This  record  shows  the  inheritance  of  artistic  ability  (black  circles  and  squares). 

(After  Davenport.) 

founder  of  Litchfield  Law  School,  herself  no  mean  lawyer  ;  Daniel 
Tyler,  a  general  in  the  Civil  War  and  founder  of  the  iron  indus- 
tries of  North  Alabama ;  Timothy  Dwight,  second,  president  of 
Yale  University  from  1886  to  1898 ;  Theodore  AVilliam  Dwight, 
founder  and  for  thirty-three  years  warden  of  Columbia  Law 
School ;  Henrietta  Frances,  wife  of  Eli  Whitney,  inventor  of  the 
cotton  gin,  who,  burning  the  midnight  oil  by  the  side  of  her  ingen- 
ious husband,  helped  him  to  his  enduring  fame ;  Merrill  Edwards 
Gates,  president  of  Amherst  College ;  Catherine  Maria  Sedg- 
wick of  graceful  pen ;  Charles  Sedgwick  Minot,  authority  on 
biology  and  embryology  in  the  Harvard  Medical  School ;  Edith 
Kermit  Carow,  wife  of  Theodore  Roosevelt ;  and  Winston  Churchill, 
the  author  of  Coniston  and  other  well-known  novels." 

Of  the  daughters  of  Elizabeth  Tuttle  distinguished  descendants 
also  came.  Robert  Treat  Paine,  signer  of  the  Declaration  of 
Independence;  Chief  Justice  of  the  United  States  Morrison  R. 
Waite ;  Ulysses  S.  Grant  and  Grover  Cleveland,  presidents  of  the 
United  States.  These  and  many  other  prominent  men  and  women 
can  trace  the  characters  which  enabled  them  to  occupy  the  posi- 
tions of  culture  and  learning  they  held  back  to  Elizabeth  Tuttle. 

Euthenics.  —  Euthenics,  the  betterment  of  the  environment, 
is  another  important  factor  in  the  production  of  a  stronger  race. 
The  strongest  physical  characteristics  may  be  ruined  if  the  sur- 
roundings are  unwholesome  and  unsanitary.     The  slums  of  a  city 


HEREDITY   AND   VARIATION  265 

are  "  at  once  symptom,  effect,  and  cause  of  evil."  A  city  which 
allows  foul  tenements,  narrow  streets,  and  crowded  slums  to  exist 
will  spend  too  much  for  police  protection,  for  charity,  and  for 
hospitals. 

Every  improvement  in  surroundings  means  improvement  of  the 
chances  of  survival  of  the  race.  In  the  spring  of  1913  the  health 
department  and  street-cleaning  department  of  the  city  of  New 
York  cooperated  to  bring  about  a  ''  clean  up  "  of  all  filth,  dirt,  and 
rubbish  from  the  houses,  streets,  and  vacant  lots  in  that  city.  Dur- 
ing the  summer  of  1913  the  health  department  reported  a  smaller 
percentage  of  deaths  of  babies  than  ever  before.  We  must  draw 
our  own  conclusions.  Clean  streets  and  houses,  clean  milk  and 
pure  water,  sanitary  housing,  and  careful  medical  inspection  all 
do  their  part  in  maintaining  a  low  rate  of  illness  and  death,  thus 
reacting  upon  the  health  of  the  citizens  of  the  future.  It  will  be 
the  purpose  of  the  following  pages  to  show  how  we  may  best  care 
for  our  own  bodies  and  how  we  may  better  the  environment  in 
which  we  are  placed. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Bailey,  Plant  Breeding.     Macmilian  and  Company. 
Harwood,  New  Creations  in  Plant  Life,     The  MacmUIan  Company. 
Jordan,  The  Heredity  of  Richard  Roe.     American  Unitarian  Association. 
Sharpe,  Laboratory  Manual,  pp.  64-72,  345-347.    American  Book  Company. 

ADVANCED 

Allen,  Civics  and  Health.     Ginn  and  Company. 

Coulter,  Castle,  East,  Tower,  and  Davenport;  Heredity  and  Eugenics.     University  of 

Chicago  Press. 
Davenport,  Heredity  in  RelatioJi  to  Eugenics.     Henry  Holt  and  Company. 
De  Vries,  Plant  Breeding.     Open  Court  Publishing  Company. 
Goddard,  The  Kallikak  Family.     The  Macmilian  Company. 
Kellicott,  The  Social  Direction  of  Human  Evolution.     Appleton  Company. 
Punnet,  Mendelism.     The  Macmilian  Company. 

Richards,  Helen  M.     Euthenics,  the  Science  of  Controllable  Environment. 
Walter,  Genetics.     The  Macmilian  Company. 


XVIII.     THE   HUMAN   MACHINE  AND   ITS   NEEDS 

Problem,—  To  obtain  a  general  understanding  of  the  parts 
and  uses  of  the  bodily  machine. 

Laboratory  Suggestions 

Demonstration.  —  Review  to  show  that  the  human  body  is  a  complex  ot 
cells. 

Laboratory  demonstration  by  means  of  (a)  human  skeleton  and  (6) 
manikin  to  show  the  position  and  gross  structure  of  the  chief  organs  of 
man. 

Man  and  his  Environment.  —  In  the  last  chapter  we  saw  that 
one  factor  in  the  improvement  of  man  lies  in  giving  him  better 
surroundings.  It  will  be  the  purpose  of  the  following  chapters 
to  show  how  man  is  fitted  to  live  in  the  environment  in  which 
he  is  placed.  He  comes  in  contact  with  air,  light,  water,  soil, 
food,  and  shelter  which  make  his  somewhat  artificial  environment ; 
he  must  adapt  himself  to  get  the  best  he  can  out  of  this  environ- 
ment. 

The  Needs  of  Living  Things.  —  We  have  already  found  that  the 
primary  needs  of  plants  and  animals  are  the  same.  They  both 
need  food,  they  both  need  to  digest  their  food  and  to  have  it  cir- 
culate in  a  fluid  form  to  the  cells  where  it  will  be  used.  They 
both  need  oxygen  so  as  to  release  the  energy  locked  up  in  their 
food.  And  they  both  need  to  reproduce  so  that  their  kind  may  be 
continued  on  the  earth.  What  is  true  of  plants  and  other  animals 
is  true  of  man. 

The  Needs  of  Simple  and  Complex  Animals  the  Same.  — 
The  simplest  animal,  a  single  cell,  has  the  same  needs  as  the  most 
complex.  The  cell  paramoecium  feeds,  digests,  oxidizes  its  food, 
and  releases  energy.  The  cells  of  the  human  body  built  up  into 
tissues  have  the  same  needs  and  perform  the  same  functions  as 
the  paramoecium.     It  is  the  cells  of  the  body  working  together 

266 


THE  HUMAN  MACHINE 


2r,7 


in  groups  as  tissues  and  organs  that  make  the  complicated  actions 
of  man  possible.  Division  of  labor  has  arisen  because  of  the 
complex  needs  and  work  of  the  organism. 

The  Human  Body  a  Machine.  —  In  all  animals,  and  the  human 
animal  is  no  exception,  the  body  has  been  likened  to  a  macliine 
in  that  it  turns  over  the  latent  or  potential 
energy  stored  up  in  food  into  kinetic 
energy  (mechanical  work  and  heat), 
which  is  manifested  when  we  perform 
work.  One  great  difference  exists  be- 
tween an  engine  and  the  human  body. 
The  engine  uses  fuel  unlike  the  substance 
out  of  which  it  is  made.  The  human 
body,  on  the  other  hand,  uses  for  fuel 
the  same  substances  out  of  which  it  is 
formed ;  it  may,  indeed,  use  part  of  its 
own  substance  for  food.  It  must  as  well 
do  more  than  purely  mechanical  work. 
The  human  organism  must  be  so  deli- 
cately adjusted  to  its  surroundings  that 
it  will  react  in  a  ready  manner  to  stimuli 
from  without ;  it  must  be  able  to  utilize 
its  fuel  (food)  in  the  most  economical 
manner ;  it  must  be  fitted  with  machinery 
for  transforming  the  energy  received  from 
food  into  various  kinds  of  work ;  it  must 
properly  provide  the  machine  with  oxygen 

so  that  the  fuel  will   be  oxidized,  and  the    The  human  body  seen  from 

products  of   oxidation  must   be   carried       the   side   in    iongitudin:U 

section. 

away,  as  well  as  other  waste  materials 

which   might    harm    the    effectiveness   of    the   machine.      Most 

important  of   all,   the   human  machine  must  be  able  to   repair 

itself. 

In  order  to  understand  better  this  complicated  machine,  the 
human  body,  let  us  briefly  examine  the  structure  of  its  parts 
and  thus  get  a  better  idea  of  the  interrelation  of  these  parts  and 
of  their  functions. 


268 


THE  HUMAN  MACHINE 


The  Skin.  —  Covering  the  body  is  a  protective  structure  called 
the  skin.  Covered  on  the  outside  with  dead  cells,  yet  it  is  provided 
with  delicate  sense  organs,  which  give  us  perception  of  touch,  taste, 

smell,  pressure,  and  temperature. 
It  also  aids  in  getting  wastes  out 
of  the  body  by  means  of  its  sweat 
glands  and  plays  an  important  part 
in  equalizing  the  temperature  of 
the  body. 

Bones  and  Muscles.  —  The  body 
is  built  around  a  framework  of 
bones.  These  bones,  which  are 
bound  together  by  tough  ligaments, 
fall  naturally  into  two  great  groups, 
the  bones  of  the  body  proper,  verte- 
bral column,  ribs,  breast  bone,  and 
skull,  which  form  the  axial  skeleton, 
and  the  appendages,  two  sets  of 
bones  which  form  the  framework 
of  the  arms  and  legs,  which  with 
the  bones  which  attach  them  to  the 
axial  skeleton  form  the  appendicular 
skeleton. 

To  the  bones  are  attached  the 
muscles  of  the  body.  Movement 
is  accomplished  by  contraction  of 
muscles,  which  are  attached  so  as 
to  cause  the  bones  to  act  as  levers. 
~p/  Bones  also  protect  the  nervous 
system  and  other  delicate  organs. 
Thej^  also  help  to  give  form  and 
rigidity  to  the  body. 

Hygiene  of  Muscles  and  Bones. 
—  Young  people  especially  need  to 
know  how  to  prevent  certain  defects 
which  are  largely  the  result  of  bad 
habits  of  posture.     Standing  erect 


cramum ; 
sternum ; 
vertebral 


Skeleton  of  a  man.  CR 
CL.,  clavicle ;  ST., 
H.,  humerus;  V.C., 
column;  R.,  radius;  U.,  ulna; 
P.,  pelvic  girdle;  C,  carpals; 
M.,  metacarpals;  Ph.,  phalanges; 
F.,  femur  ;  Fi.,  fibula  ;  T.,  tibia  ; 
Tar.,  tarsals;  MT.,  metatar- 
sals. 


THE   HUMAN   MACHINE 


269 


is  an  example  of  a  good  habit,  round  shoulders  a  bad  habit  of  this 
sort.  The  habit  of  a  wrong  position  of  bones  and  muscles  once 
formed  is  very  hard  to  correct. 
This  can  best  be  done  by  certain 
corrective  exercises  at  home  or 
in  the  gymnasium. 

Round  shoulders  is  most  com- 
mon among  people  whose  occu- 
pation causes  them  to  stoop. 
Prawing,  writing,  and  a  wrong 
position  when  at  one's  desk  are 
among  the  causes.  Exercises 
which  strengthen  the  back 
muscles  and  cause  the  head  to 
be  kept  erect  are  helpful  in  form- 
ing the  habit  of  erect  carriage. 

Slight  curvature  of  the  spine 
either  backward  or  forward  is 
helped  most  by  exercises  which 
tend  to  straighten  the  body, 
such  as  stretching  up  with  the 
hands  above  the  head.  Lateral  curvature  of  the  spine,  too  often 
caused  by  a  *'  hunched-up  "  position  at  the  school  desk,  may  also 


Diagram  showing  action  of  biceps  muscle. 
a,  contracted;  6,  extended;  h,  humerus; 
s,  scapula. 


w 


F 


4 


A  B  C 

Three  classes  of  levers  in  the  human  body;  bones  and  muscles  act  together. 
A,  a  lever  of  the  first  class;  B,  a  lever  of  the  second  class ;  C,  a  lever  of  the 
third  class. 

be   corrected    by   exercises   which   tend    to   lengtlien   the   spinid 
column. 

It  is  the  duty  of  every  girl  and  boy  to  have  good  posture  and 


270 


THE   HUMAN  MACHINE 


Bad  posture  iu  the 
schoolroom  may 
cause  permanent 
injury  to  the  spine. 


erect  carriage,  not  only  because  of  the  better 
state  of  health  which  comes  with  it,  but  also 
because  one's  self-respect  demands  that  each 
one  of  us  makes  the  best  of  the  gifts  that 
nature  has  given  us.  An  erect  head,  straight 
shoulders,  and  elastic  carriage  go  far  toward 
making  their  owner  both  liked  and  respected. 

Other  Body  Structures.  —  In  spaces  between 
the  muscles  are  found  various  other  structures, 
—  blood  vessels,  which  carry  blood  to  and  from 
the  great  pumping  station,  the  heart,  and 
thence  to  all  parts  of  the  body ;  connective 
tissue,  which  holds  groups  of  muscle  or  other 
cells  together ;  fat  cells,  scattered  in  various  parts  of  the  body ; 
various  gland  cells,  which  manufacture  enzymes ;  and  the  cells 
of  the  nervous  system,  which  aid  in  directing  the  body  parts. 

Body  Cavity.  —  Within  the  body  is  a  cavity,  which  in  life  is 
almost  completely  filled  with  various  organs.  A  thin  wall  of 
muscle  called  the  diaphragm  divides  the  body  cavity  into  two 
unequal  spaces.  In  the  upper  space  are  found  the  heart  and  lungs, 
in  the  lower,  the  digestive  tract  with  its  glands,  the  liver,  kidneys, 
and  other  structures  (see  page  267). 

Digestion,  Absorption,  and  Excretion.  —  Running  through  the 
body  is  a  food  tube  in  which  undigested  food  is  placed  and  from 
which  digested  or  liquid  food  is  absorbed  into  the  blood  so  that  the 
cells  of  the  various  organs  which  do  the  work  may  receive  food. 
Emptying  into  this  food  tube  are  various  groups  of  gland  cells, 
which  pour  digestive  fluids  over  the  solid  foods,  thus  aiding  in 
changing  them  to  liquids.  Solid  wastes  are  passed  out  through 
the  posterior  end  of  the  food  tube,  while  liquid  wastes  are  excreted 
by  means  of  glands  called  kidneys. 

Work  done  by  Cells.  —  Food,  prepared  in  the  digestive  tract, 
and  oxygen  from  the  lungs  are  taken  by  the  blood  to  the  cells. 
Bathed  in  liquid  food,  the  cells  do  their  work;  they  promote 
the  oxidization  of  food  and  the  exchange  of  carbon  dioxide  for 
oxygen  in  the  blood,  while  other  wastes  of  the  cells  are  given  off, 
to  pass  eventually  through  the  kidneys  and  out  of  the  body. 


THE   HUMAN   MACHINE  271 

The  Nervous  System.  —  The  smooth  working  of  the  bodily 
machine  is  due  to  another  set  of  structures  which  direct  the  work- 
ing of  the  parts  so  that  they  will  act  in  unison.  This  director  is 
the  nervous  system.  We  have  seen  that,  in  the  simplest  of  animals, 
one  cell  performs  the  functions  necessary  to  its  existence.  In 
the  more  complex  animals,  where  groups  of  cells  form  tissues, 
e^ch  having  a  different  function,  a  nervous  system  is  developed. 
The  functions  of  the  human  nervous  system  are  :  (1)  the  providing 
of  man  with  sensation,  by  means  of  which  he  gets  in  touch  with  the 
world  about  him;  (2)  the  connecting  of  organs  in  different  parts  of 
the  body  so  that  they  act  as  a  united  and  harmonious  whole;  (3)  the 
giving  to  the  human  being  a  will,  a  provision  for  thought.  Cooper- 
ation in  word  and  deed  is  the  end  attained.  We  are  all  familiar 
with  examples  of  the  cooperation  of  organs.  You  see  food ;  the 
thought  comes  that  it  is  good  to  eat ;  you  reach  out,  take  it,  raise 
it  to  the  mouth ;  the  jaws  move  in  response  to  your  will ;  the  food 
is  chewed  and  swallowed.  While  digestion  and  absorption  of  the 
food  are  taking  place,  the  nervous  system  is  still  in  control.  The 
nervous  system  also  regulates  pumping  of  blood  over  the  body, 
respiration,  secretion  of  glands,  and,  indeed,  every  bodily  function. 
Man  is  the  highest  of  all  animals  because  of  the  extreme  develop- 
ment of  the  nervous  system.  Man  is  the  thinking  animal,  and  as 
such  is  master  of  the  earth. 

Reference  Reading  for  This  and  Succeeding  Chapters  on  Human  Biology 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Davison,  The  Human  Body  and  Health.     American  Book  Company. 

Gulick,  The  Gulick  Hygiene  Series.     Ginn  and  Company. 

Overton,  General  Hygiene.     American  Book  Company. 

Ritchie,  Human  Physiology.     World  Book  Company. 

Sharpe,  Laboratory  Manual  in  Botany,  pages  218-225.     American  Book  Company. 

advanced 

Halliburton,  Kirk's  Handbook  of  Physiology.     P.  Blakiston's  Son  and  Company. 
Hough  and  Sedgwicic,  The  Human  Mechanism.     Ginn  and  Company. 
Howell,  Physiology,  3d  edition.     W.  B.  Saunders  Company. 
Schafer,  Textbook  of  Physiology.     The  Macmillan  Company. 
Stiles,  Nutritional  Physiology.    W.  B.  Saunders  Company. 
Verworn,  General  Physiology.     The  Macmillan  Company. 


y 


XIX.     FOODS   AND   DIETARIES 

Prohle^ns,  —  A  study  of  foods  to  determine:  — 

(a)  Their  nutritive  value. 

(b)  The  relation  of  worh,  environment,  age,  sex,  and  digef<- 
tihility  of  foods  to  diet.     ■  ' 

(c)  Their  relative  cheapness. 

id)   The  daily  Calorie  requirement. 

ie)   Food  adulteration. 

(/)  TJie  relation  of  alcohol  to  the  human  system. 

Laboratory  Suggestions 

Laboratory  exercise.  —  Composition  of  common  foods.  The  series  of 
food  charts  supplied  by  the  United  States  Department  of  Agriculture 
makes  an  excellent  basis  for  a  laboratory  exercise  to  determine  common 
foods  rich  in  (a)  water,  (6)  starch,  (c)  sugar,  {d)  fats  or  oils,  (e)  protein, 
(/)  salts,  {g)  refuse. 

Demonstration.  —  Method  of  using  bomb  calorimeter. 

Laboratory  and  home  exercise.  —  To  determine  the  best  individual  bal- 
anced dietary  (using  standard  of  Atwater,  Chittenden,  or  Voit)  as  deter- 
mined by  the  use  of  the  100-Calorie  portion. 

Demonstration.  —  Tests  for  some  common  adulterants. 

Demonstration.  —  Effect  of  alcohol  on  protein,  e.g.  white  of  Qgg. 

Demonstration.  —  Alcohol  in  some  patent  medicines. 

Demonstration.  —  Patent  medicines  containing  acetanilid.  Determina- 
tion of  acetanilid. 

Why  we  Need  Food.  —  A  locomotive  engine  takes  coal,  water, 
oxygen,  from  its  environment.  A  living  plant  or  animal  takes 
organic  food,  water,  and  oxygen  from  its  environment.  Both  the 
living  and  nonliving  machine  does  the  same  thing  with  this  fuel 
or  food.  They  oxidize  it  and  release  the  energy  in  it.  But  the 
living  organism  in  addition  may  use  the  food  to  repair  parts  that 
have  broken  down  or  even  build  new  parts.  Thus  food  may  he 
defined  as  something  that  releases  energy  or  that  forms  material  for 

272 


water 


FOODS   AND   DIETARIES  273 

the  growth  or  repair  of  the  body  of  a  plant  or  animal.  The  mil- 
lions of  cells  of  which  the  body  is  composed  must  be  given  material 
which  will  form  more  living  matter  or  material  which  can  be  oxi- 
dized to  release  energy  when  muscle  cells  move,  or  gland  cells 
secrete,  or  brain  cells  think. 

Nutrients.  —  Certain  nutrient  materials  form  the  basis  of  food 
of  both  plants  and  animals.  These  have  been  stated  to  be  proteins 
(such  as  lean  meat,  eggs,  the  gluten  of  bread), 
carbohydrates  (starches,  sugars,  gums,  etc.),  fats 
and  oils  (both  animal  and  vegetable),  mineral  ^f^r^sr^Asuaar 
matter  and  water.  B^^^Kprotoid 

Proteins.  —  Protein  substances  contain  the 
element  nitrogen.  Hence  such  foods  are  called 
nitrogenous  foods.  Man  must  form  the  proto- 
plasm of  his  body  (that  is,  the  muscles,  tendons, 
nervous  system,  blood  corpuscles,  the  living  parts 
of  the  bone  and  the  skin,  etc.)  in  part  at  least 
from  nitrogenous  food.  Some  of  this  he  ob-  ThcTcomiiosition  of 
tains  by  eating  the  flesh  of  animals,  and  some      niiik.     why  is  it 

11..  ]•        xi       r  1       J.       /r  1  considered  a  good 

he  obtams  directly  irom  plants   (tor  example,      food? 

peas  and  beans).     Proteins  are  the  only  foods 

directly  available  for  tissue  building.     They  may  be  oxidized  to 

release  energy  if  occasion  requires  it. 

Fats  and  Oils.  —  Fats  and  oils,  both  animal  and  vegetable, 
are  the  materials  from  which  the  body  derives  part  of  its  energy. 
The  chemical  formula  of  a  fat  shows  that,  compared  with  other 
food  substances,  there  is  very  little  oxygen  present ;  hence  the 
greater  capacity  of  this  substance  for  uniting  with  oxygen.  The 
rapid  burning  of  fat  compared  with  the  slower  combustion  of  a 
piece  of  meat  or  a  piece  of  bread  illustrates  this.  A  pound  of  butter 
releases  over  twice  as  much  energy  to  the  body  as  does  a  pound  of 
sugar  or  a  pound  of  steak.  Human  fatty  tissue  is  formed  in  part 
from  fat  eaten,  but  carbohydrate  or  even  protein  food  may  be 
changed  and  stored  in  the  body  as  fat. 

Carbohydrates.  —  We  see  that  the  carbohydrates,  like  the  fats, 
contain  carbon,  hydrogen,  and  oxygen.  Carbohydrates  are  essen- 
tially energy-producing  foods.     They  are,  however,  of  use  in  build- 

HUNTER,    CIV.    BI. 18 


r  cr)m 
%.  meaJ 
\  2lbs. 


274  FOODS   AND  DIETARIES 

ing  up  or  repairing  tissue.  It  is  certainly  true  that  in  both  plants 
and  animals  such  foods  pass  directly,  together  with  foods  contain- 
ing nitrogen,  to  repair  waste  in  tissues,  thus  giving  the  needed 
proportion  of  carbon,  oxygen,  and  hydrogen  to  unite  with  the 
nitrogen  in  forming  the  protoplasm  of  the  body. 

Inorganic  Foods.  —  Water  forms  a  large  part  of  almost  every 
food  substance.     It  forms  about  five  sixths  of  a  normal  daily  diet. 

The  human  body,  by  weight,  is 
about  two  thirds  water.  About  90 
per  cent  of  the  blood  is  water. 
Water  is  absolutely  essential  in 
passing  off  waste  of  the  body. 
When  we  drink  water,  we  take 
Ycents^      v^^^  '\r      with  it  some  of  the  inorganic  salts 

used  by  the  body  in  the  making  of 
Three  portions  of  foods,  each   of  bone  and  in  the  formation  of  proto- 

which   furnishes    about    the    same       j^gj^^         Sodium     chloride      (table 
amount  of  nourishment.  ^  ^ 

salt),  an  important  part  of  the 
blood,  is  taken  in  as  a  flavoring  upon  our  meats  and  vegetables. 
Phosphate  of  lime  and  potash  are  important  factors  in  the  forma- 
tion of  bone. 

Phosphorus  is  a  necessary  substance  for  the  making  of  living 
matter,  milk,  eggs,  meat,  whole  wheat,  and  dried  peas  and  beans 
containing  small  amounts  of  it.  Iron  also  is  an  extremely  impor- 
tant mineral,  for  it  is  used  in  the  building  of  red  blood  cells.  Meats, 
eggs,  peas  and  beans,  spinach,  and  prunes,  are  foods  containing 
some  iron. 

Some  other  salts,  compounds  of  calcium,  magnesium,  potassium, 
and  phosphorus,  have  been  recently  found  to  aid  the  body  in  many 
of  its  most  important  functions.  The  beating  of  the  heart,  the 
contraction  of  muscles,  and  the  ability  of  the  nerves  to  do  their 
work  appear  to  be  due  to  the  presence  of  minute  quantities  of  these 
salts  in  the  body. 

Uses  of  Nutrients.  —  The  following  table  sums  up  the  uses  of 
nutrients  to  man  :  ^  — 

^  Adapted  from  Atwater,  Principles  of  Nutrition  and  Nutritive  Value  of  Food 
U.S.  Department  of  Agriculture,  1902. 


FOODS   AND   DIETARIES 


275 


All  serve  as 
fuel  and  yield 
energy  in  form 
of  heat  and  mus- 
cular       strength. 


Protein Forms  tissue   (mus- 

White   of   eggs    (albumen),  cles,        tendon, 

curd  of  milk  (casein),  lean  and      probably 

meat,  gluten  of  wheat,  etc.  fat). 

Fats    .     .  ■ .     Form  fatty  tissue. 

Fat  of  meat,  butter,  olive  oil, 
oils  of  corn  and  wheat,  etc. 

Carbohydrates Transformed       into 

Sugar,    starch,    etc.  fat. 

Mineral   matters    (ash).     .     .     Aid  in  forming  bone, 
Phosphates  of  Ume,  potash,  assist   in   diges- 

soda,    etc.  tion,  aid  in  ab- 

sorption and  in 
other  ways  help 
the  body  parts 
do  their  work. 
Water  used  as  a  vehicle  to  carry  nutrients,  and  enters  into  the  compo- 
sition of  living  matter. 

Common  Foods  contain  the  Nutrients.  —  We  have  already 
found  in  our  plant  study  that  various  plant  foods  are  rich  in  dif- 
ferent nutrients,  carbohydrates  forming  the  chief  nutrient  in  the 
foods  we  call  cereals,  breads,  cake,  fleshy  fruits,  sugars,  jellies,  and 
the  like.  Fats  and  oils  are  most  largely  found  in  nuts  and  some 
grains.  Animal  foods  are  our  chief  supply  of  protein.  White  of 
egg  and  lean  meat  are  almost  pure  protein  and  water.  Proteins 
are  most  abundant,  as  we  should  expect,  in  those  plants  which  are 
richly  supplied  with  nitrogen ;  peas  and  beans,  and  in  grains  and 
nuts.  Fats,  which  are  melted  into  oils  at  the  temperature  of  the 
body,  are  represented  by  the  fat  in  meats,  bacon,  pork,  lard, 
butter,  and  vegetable  oils. 

Water.  —  Water  is,  as  we  have  seen,  a  valuable  part  of  food. 
It  makes  up  a  very  high  percentage  of  fresh  fruits  and  vegetables ; 
it  is  also  present  in  milk  and  eggs,  less  abundant  in  meats  and  fish, 
and  is  lowest  in  dried  foods  and  nuts.  The  amount  of  water  in  a 
given  food  is  often  a  decided  factor  in  the  cost  of  the  given  food, 
as  can  easily  be  seen  by  reference  to  the  chart  on  page  283. 

Refuse.  —  Some  foods  bought  in  the  market  may  contain  a 
certain  unusable  portion.      This   we  call    refuse.      Examples  of 


276 


FOODS  AND   DIETARIES 


DIGESTIBLE  NUTRIENTS 


INDIGESTIBLE 
NUTRIENTS 


HON  NUTRIENTS 


PROTEIN 

MUSCLE 
MAKING 


FATS 


CARBO-       MINERAL 
HYDRATE^  MATTERS 


WATER        REFUSE 


^      FUEL   VALUE 
CALORIES 


FUEL  INGREDIENTS 


NUTRIENTS,  ETC., 
PER  CENT. 


FUEL  VALUE  OP 

1  LB.    ("-ALriRIEs) 


Milk, 
unskimmed 

Butter 


■White  bread 


Oat  meal 


Corn  meal 


Rice 


10 

— 1 — 


20 


30 


40 


50 


60 


70 


80 

— r- 


90 


100 


400 


800 


1,200      2.000     2.200      2,400      2,800     3,200   3,600  4.000 


m 


Tabic  of  food  values.  Determine  the  percentage  of  water  in  codfish,  loin  of  beef, 
mUk,  potatoes.  Percentage  of  refuse  in  leg  of  mutton,  codfish,  eggs,  and 
potatoes.  What  is  the  refuse  in  each  case  ?  Find  three  foods  containing  a 
high  percentage  of  protein  ;  of  fat ;  of  carbohydrate.  Find  some  food  in 
which  the  proportions  of  protein,  fat,  and  carbohydrate  are  combined  in  a 
good  proportion. 


FOODS  AND   DIETARIES  277 

refuse  are  bones  in  meat,  shells  of  eggs  or  of  shellfish,  the  covering 
of  plant  cells  which  form  the  skins  of  potatoes  or  other  vegetables. 
The  amount  of  refuse  present  also  plays  an  important  part  in  the 
values  of  foods  for  the  table.  The  table  ^  on  page  276  gives  the  per- 
centages of  organic  nutrients,  water,  and  refuse  present  in  some 
common  foods. 

Fuel  Values  of  Nutrients.  —  In  experiments  performed  by 
Professor  Atwater  and  others,  and  in  the  appended  tables,  the 
value  of  food  as  a  source  of  energy  is  stated  in  heat  units  called 
Calories.  A  Calorie  is  the  amount  of  heat  required  to  raise  the  tem- 
perature of  one  kilogram  of  water  from  zero  to  one  degree  Centigrade. 
This  is  about  equivalent  to  raising  one  pound  four  degrees  Fahren- 
heit. The  fuel  value  of  different  foods  may  be  computed  in  a 
definite  manner.  This  is  done  by  burning  a  given  portion  of  a 
food  (say  one  gram)  in  the  apparatus  known  as  a  calorimeter. 
By  this  means  may  be  determined  the  number  of  degrees  the 
temperature  of  a  given  amount  of  water  is  raised  during  the  process 
of  burning.  It  has  thus  been  found  that  a  gram  of  fat  will  liber- 
ate 9.3  Calories  of  heat,  while  a  gram  of  starch  or  sugar  only  about 
4  Calories.  The  burning  value  of  fat  is,  therefore,  over  twice  that 
of  carbohydrates.  In  a  similar  manner  protein  has  been  shown  to 
have  about  the  same  fuel  value  as  carbohvdrates,  i.e.  4  Calories 
to  a  gram.^ 

The  Relation  of  Work  to  Diet.  —  It  has  been  shown  experimen- 
tally that  a  man  doing  hard,  muscular  work  needs  more  food 
than  a  person  doing  light  work.  The  mere  exercise  gives  the 
individual  a  hearty  appetite ;  he  eats  more  and  needs  more  of 
all  kinds  of  food  than  a  man  or  boy  doing  light  work.  Especially 
is  it  true  that  the  person  of  sedentary  habits,  who  does  brain  work, 
should  be  careful  to  eat  less  food  and  food  that  will  digest  easily. 
His  protein  food  should  also  be  reduced.  Rich  or  hearty  foods 
may  be  left  for  the  man  w^ho  is  doing  hard  manual  labor  out 
of  doors,  for  any  extra  work  put  on  the  digestive  organs  takes 
away  just  so  much  from  the  ability  of  the  brain  to  do  its 
work. 

1  W.  O.  Atwater,  Principles  of  Nutrition  and  Nutritive  Value  of  Food,  U.S.  De- 
partment of  Agriculture,  1902. 


278 


FOODS   AND   DIETARIES 


O^ict  of  CwcrimtAi  Stittoni 
A.C.  True-  Difcctor 


9ttp«rta  oj 

C.  f.WAHGWORTHY 

tapert  in  Cha<«c  0'  Nutr>t>or>  Inveshjitictns 


COMPOSITION  OF  FOOD  MATERIALS. 


■■      I      I      I      I      r~    1      fts?! 


SHELLED  BEAN,   FRESH 

'jter  58.9 
fit.0.6 


Pruu;n9.4 


lOOO  Catoi 


NAVY    BEAN,   DRY 

Waierl?6 

bohydrite&.29.l 

.  t.ojj  Carbohydrates  59.6 


STRING   BEAN,  GREEN. 

^Csrbohydrates:  7.'t >"«?       Aih'.O.B 

Water.89.? 


Wsier75.4 


l90c*i.oii(»  PtnPouiiD 
CORN,    GREEN. 

tOlBLt  PORTION 

P^olelr^  3   I  - 


Carbohyorales:  19.7 
(JM   -Ash;0.7 


Fat-.l.l 


U.S.Oep^rmcAi  of  Agriculture 

Officf  o1  Ei^Mhnicnt  Sulior\$ 

AC.  True,  director 


Prepared  bj 
C.  f.  imiswoaTHY 
Eipert  In  Chir9e  of  Nulriljon  Intestigitiot^s 


COMPOSITION  OF  FOOD  MATERIALS. 


r^t  Cjrbohyd'4U3 


Fuel  Vatut 

b  Sq.ln.EQutJf 

000  Calortvt 


P<atnr>  r^t  Cjfbohyd<*l«         A»h  Water 

WHITE  BREAD  WHOLE  WHEAT  BREAD 

_Waier:35.3    Water 

^Protein:  9  2     Protein 

Carbo-  Carfao 

hydrates:  63.  r    hydrate 


fl«i    ViiuE: 


OAT 
BREAKFAST     FOOD 


Fufl    WLUE: 


lieOaLomj      Water-84.5 
Protein;2.8 

TOASTED  BREAD 

Ash-.O 


I  t  t  0  CALOftltS 
>C>I  POUiO 

.Fat:0.5 

Carbohydrates'  11.5 

CORN  BREAD 


FufL 


280cALORr£S 

PER  POUND 


Water:  ?4.0        Waler:38.9 
Proteiri:  11.5        Protein:  7  9 


_arbo-  Carbo- — '     \----:y---''.':'-l  Ash: 

(hydrate3:6l.2  hydrate5:*63    \sizzZ^z^z&^ i  2 

Fut^rjLut:  MACARONI  Futi_«u,E, 

^^^H  COOKED 

1^1        Fat.  1.6^  Proteln:3.0 
t380c4LO»'ES 

PfBPOWO   ^ ■ 

Ash:  1.3;^     '" 
.•^  F, 


-Water-78.4 


1 1 75cj»L0B(ia 

PfR POUIO 


Carbo' 
hydrates:  15.8 


VALUE 


c 


400uu)Bies 
peopouHt} 


U.  J.  tk^A'tmeol  o'  AfliScwHwie  Prepared  br 

OH.ce  ot  (*p**imefil  StJl'Ofti  C.  F.  LJltGWORTHY 

K  C.  True:  C^'eetc  Cipct  in  Charqe  ol  Mutritior^  Investiqatiom 

COMPOSITION  OF  FOOD   MATERIALS 

^^     rniTmiii     rm  ^^     ^a 

Prott-n                Fat          Carbohydrate  AiK                  Water 


^tSq  In  Equals 
1000  Calone: 


ONION 


Carbohydrates:9  9- 
-Water  83  0  Fuji    „ius, 


Prole!n:1.6 
F8t.0.5 
arboKydrates;l3.5 


«!.hl4 


PARSNIP 


Water945 


Carbohydrates:  I3  4    ^Waier:78  3 

FueiMLUf:  Protein:  1.1 

I    J  Carbohydrates:  3.4 

37j  caLoails  Pfer>ouaO  A^:|.0 


li.  S.  Department  ot  Agriculture 
Oftite  ot  f  xpetiment  Stations 
A.  C.  True;  Director 


Prepared  by 

C.  F.UUIGWOSIMY 

I  spert  in  Cturge  ot  Notrrtion  InvestlgatioBS 


COMPOSITION  OF  FOOD  MATERIALS. 


F'at  Carbohydrate)         Ash 


JCarboh^drates  lOO-O 


■    Cual  Value 
'^fcSq  lr>.Equdlj 
1000  Calpnas 

MOLASSES 


Prote;n:2.4 


Water:2J.I 


Carbohydrates  693 


STICK  CANDY 


1810  CAtooits  ^ Carbohydrates: %  5 


FufL  vAiuC: 


I300CAL0HIES 

PfRPOUIP 


Watet:3.0 


MAPLE  SUGAR 


FOEL    VaiuE: 


1745  aLoitiES 

PEH POUND 


Ash:  0.5 


HONEY 


Ash:0.9^ 


-Water:|6.3      Water:l8.2- 
Protein:0. 


Carbo-  ■  Carbo.- 

hydrates:82.8      hydrates.! 


1500 


(JLORICSPCOPOUIID 


Fuel  v*luE: 
1475  c«io«iESPfPPoun& 


Ash- 0.2 


Foods  of  plant  origin.  Select  5  foods  containing  a  high  percentage  of  protein, 
5  with  a  high  percentage  of  carbohydrates,  5  with  a  high  percentage  of  water. 
Do  vegetable  foods  contain  much  fat  ?  Which  of  the  above-mentioned  foods 
have  the  highest  burning  value? 


FOODS   AND   DIETARIES 


279 


U.S.  OtpittmenX  of  AgricuHure 

Office  ol  Etpntfneni  Sution» 

A.C.  true  0>rectoi 


Prepartd  b7 

C.r.  lAH&WOHTHY 
I  ipe't  in  Chifgt  of  Nutntron  imesbqiiioos 


COMPOSITION  OF  FOOD  MATERIALS. 


ES3 


'  (000  Ciiorm 


SALT  COD 


H|Water:5J5, 


OYSTER 

Water86  9 


400    CAIOBIIS 
*f«  POUPiO       _ 

fatO  J  — 


\[^\/     Ash.  12 

bohydfa(es*3.  ^ 


SMOKED  HERRING 


MACKEREL 

Fat  F'ih 


.Wat<rr  3*  6 

Protetn:36.4 

FuK    viiuf: 


1305     CALOHiEi 


Ash:  1 3.2' 


230  WLOOiti 


6?0  (jilorics 


U.  S.  OtM^THm  of  Afficuriwa 
Office  of  fiH^Woint  $riii«ns 


CF.UifGwOfiTNT 

(lpert>nCHV9<  0>  HutnMn  ln«cst>^4 


COMPOSITION  OF  FOOD  MATERIALS. 

CTiin     rrn     r*^     rri     ^  fv..-.!- 


t>arf»'n 


^^"  iOOOC«io«« 

LAMB  CHOP  PORK  CHOP 


tO'»lf  (>0«''0^ 


fjtJO-l 


'^  '5  ciiioBiej 
PfaDOuaD 


BEEF  STEAK 

CUBIC  Oo«T>CN 

Wdter:6 


furi 

V*IU£ 


Ash. 4  a 

1875  wtoffics 

DRIED  BEET 

Water    54  ?      y.r>w^^prot».A: 


F«t:t8.5 


8iO  uc<*o 
Ptaeogae 


CF.LANGWOBTHY 


U.S-0«P"'1'"Cnt  of  Agriculture 

Oflit*  of  I  «p«fimeftt  S'lt'ons 

A.C  ^rue:  Direttor 

COMPOSITION  OF  FOOD  MATERIALS 

Protein  Fdt  Cirb«hjd'«te»  Ash  W*ler  ^^|  *qqq  c«ioriei 

WHOLE  EGG  EGG 

WHITE  UDTOIK 


Protein 

'♦•8 
fat:lO 

Ash:  I  0 

FuFL     V«LUf    Of 

WHOLE  166'. 


Fof I  vAiut  ot  vouc 


695  ulorics 

Pt»P0UI*O 


CREAM  CHEESE 
Water  34  2 


I  bio   c«io«it5 

PIR  POUND 


Futl    VALUE    OF  wmiTE: 

c 

?45   CALOPlfS 
PER  POUND 


COTTAGE  CHEESE 


Protein:  20  9 


1665    OLORICSPERPOUIIO 


495  oioditspeRPOuiio 


U.S.  Oep»lm«m  ;>(  Agr'KuihM  PrepMrd  ») 

Off'Ct  of  Eiotfimenl  Sulioii  C.f .  iWCwOBTMt 

A.C.  Irut'  Diftctoi  (t^rl  in  D^arge  ol  Mulr>t«n  in*t3liCJt>eas 

COMPOSITION  OF  FOOD  MATERIALS. 

^^     fmiiii     r-n  E';;^m     E3     ^.  f-i  *•'- 

P'ote-r.                 ft\           C«rtohydr«tw  Ash                  Vat«i 


lOOO  C«ion« 


VEGETABLE  OILS, AS 
OLIVE  , 
PEANUT, 
COTTONSEED 


FatlOOO 


BACON 
Protein;9  4^  ^Fat:6'« 


Water  I&8 


Fat  81,8 


4080  C'L08>E5  PER  POVID 


BUTTER 

1^"'°   ^     ■Vx^Wa.enl3.0 


J090   uumri   »•  Pow« 
Water  II? 
P.oleiO:4  7 


-A»h;0.3 


34?5  c-*Lo«iis  pm  poupo 


LARD 


Ptolein;  1.0 


3405c«jnnj  PER 


♦060  oiiiiKJ  "-1"  ■^I'C 


Foods  largely  of  animal  origin.  Compare  with  the  previous  chart  with  refer- 
ence to  amount  of  protein,  carbohydrate,  and  fat  in  foods.  Compare  the 
burning  value  of  plant  and  animal  foods.  Compare  the  relative  percentage 
of  water  in  both  kinds  of  foods. 


280 


FOODS   AND   DIETARIES 


4  C.  True:  DifCCUr 


Prepvedby 

C.  F.  muGWORTHY 

U^n  In  Cunie  ol  Nutrition  Invuti^rton) 


COMPOSITION  OF  FOOD  MATERIALS. 


1000  Ca(on«i 


WHOLE  MILK 


SKtMMILK 


-Water:870 


Protein:  3.3 


Carbohydrjtes:5.0 


Vater-90.S 


Protein:  3.4 


^Ufl    ■<UU(;   3l5cUOIIISP(BP0UIID 


BUTTERMILK 


CarbohydrJtes:5.l 

c 

Fltl    »illUt:    l65c<L0«ltSPfI'»0U»B 


CREAM 


^Water  91.0 


Carbohydrates:4.8 

D 

Fuel  vuuE;  l60ciL0Bies  re»PouiB 


Protein:  3.0    Fat:  18.5- 
Ash:05' 


^Water:74.0 
Protein:2.5 


Carbo^^vdrates:4  5 


The  Relation  of  Environment  to  Diet.  —  We  are  all  aware  of  the 
fact  that  the  body  seems  to  crave  more  food  in  winter  than  in 

summer.  The  temperature  of 
the  body  is  maintained  at  98.6° 
in  winter  as  in  summer,  but 
much  more  heat  is  lost  from  the 
body  in  cold  weather.  Hence 
feeding  in  winter  should  be  for 
the  purpose  of  maintaining  our 
fuel  supply.  We  need  heat- 
producing  food,  and  we  need 
more  food  in  winter  than  in 
summer.  We  may  use  carbo- 
hydrates for  this  purpose,  as 
they  are  economical  and  diges- 
tible. The  inhabitants  of  cold 
countries  get  their  heat-releasing 
foods  largely  from  fats.  In 
tropical  countries  and  in  hot 
weather  little  protein  should 
be  eaten  and  a  considerable 
amount  of  fresh  fruit  used. 
The  Relation  of  Age  to  Diet.  —  As  we  will  see  a  little  later,  age 
is  a  factor  not  only  in  determining  the  kind  but  the  amount  of 
food  to  be  used.  Young  children  require  far  less  food  than  do 
those  of  older  gro^\i:h  or  adults.  The  body  constantly  increases 
in  weight  until  young  manhood  or  womanhood,  then  its  weight 
remains  nearly  stationary,  varying  with  health  or  illness.  It  is 
evident  that  food  in  adults  simply  repairs  the  waste  of  cells  and 
is  used  to  supply  energy.  Elderly  people  need  much  less  protein 
than  do  younger  persons.  But  inasmuch  as  the  amount  of  food 
to  be  taken  into  the  body  should  be  in  proportion  to  the  body 
weight,  it  is  also  evident  that  growing  children  do  not,  as  is  popu- 
larly supposed,  need  as  much  food  as  grown-ups. 

The  Relation  of  Sex  to  Diet.  —  As  a  rule  boys  need  more  food 
than  girls,  and  men  than  women.  This  seems  to  be  due  to,  first, 
the  more  active  muscular  life  of  the  man  and,  secondly,  to  the 


fufL    VillK:  880  OILOBlFS  "tO  PflUPlO 


The  composition  of  milk. 


FOODS  AND   DIETARIES  281 

greater  amount  of  fat  in  the  tissues  of  the  woman,  making 
loss  of  heat  less.  Larger  bodies,  because  of  greater  surface, 
give  off  more  heat  than  smaller  ones.  Men  are  usually  larger 
in  bulk  than  are  women,  —  another  reason  for  more  food  in  their 
case. 

The  Relation  of  Digestibility  to  Diet.  —  Animal  foods  in  general 
may  be  said  to  be  more  completely  digested  within  the  body  than 
plant  foods.  This  is  largely  due  to  the  fact  that  plant  cells  have 
woody  walls  that  the  digestive  juices  cannot  act  upon.  Cereals 
and  legumes  are  less  digestible  foods  than  are  dairy  products, 
meat,  or  fish.  This  does  not  mean  necessarily  that  these  foods 
would  not  agree  with  you  or  me  but  that  in  general  the  body  would 
get  less  nourishment  out  of  the  total  amount  available. 

The  agreement  or  disagreement  of  food  with  an  individual  is 
largely  a  personal  matter.  I,  for  example,  cannot  eat  raw  toma- 
toes without  suffering  from  indigestion,  while  some  one  else  can 
digest  tomatoes  but  not  strawberries.  Each  individual  should 
learn  early  in  life  the  foods  that  disagree  with  him  personally 
and  leave  such  foods  out  of  his  dietary.  For  ''  what  is  one  man's 
meat  may  be  another  man's  poison." 

The  Relation  of  Cost  of  Food  to  Diet.  —  It  is  a  mistaken  notion 
that  the  best  foods  are  always  the  most  expensive.  A  glance  at 
the  table  (page  283)  will  show  us  that  both  fuel  value  and  tissue- 
building  value  is  present  in  some  foods  from  vegetable  sources,  as 
well  as  in  those  from  animal  sources,  and  that  the  vegetable  foods 
are  much  cheaper.  The  American  people  are  far  less  economical 
in  their  purchase  of  food  than  most  other  nations.  Nearly  one 
half  of  the  total  income  of  the  average  workingman  is  spent  on 
food.  Not  only  does  he  spend  a  large  amount  on  food,  but  he 
wastes  money  in  purchasing  the  wrong  kinds  of  food.  A  compari- 
son of  the  daily  diets  of  persons  in  various  occupations  in  this 
and  other  countries  shows  that  as  a  rule  we  eat  more  than  is  nec- 
essary to  supply  the  necessary  fuel  and  repair,  and  that  our  working- 
men  eat  more  than  those  of  other  countries.  Another  waste  of 
money  by  the  American  is  in  the  false  notion  that  a  large  ])ro])or- 
tion  of  the  daily  dietary  should  be  meat.  Many  ])c()])le  think 
that  the  most  expensive  cuts  of  meat  are  the  most  nutritious. 


282  FOODS  AND   DIETARIES 

The  falsity  of  this  idea  may  be  seen  by  a  careful  study  of  the  tables 
on  pages  283  and  286. 

The  Best  Dietary.  —  Inasmuch  as  all  living  substance  contains 
nitrogen,  it  is  evident  that  protein  food  must  form  a  part  of  the 
dietary  ;  but  protein  alone  is  not  usable.  If  more  protein  is  eaten 
than  the  body  requires,  then  immediately  the  liver  and  kidneys 
have  to  work  overtime  to  get  rid  of  the  excess  of  protein  which 
forms  a  poisonous  waste  harmful  to  the  body.  We  must  take 
foods  that  will  give  us,  as  nearly  as  possible,  the  proportion  of 
the  different  chemical  elements  as  they  are  contained  in  proto- 
plasm. It  has  been  found,  as  a  result  of  studies  of  Atwater  and 
others,  that  a  man  who  does  muscular  work  requires  a  little  less 
than  one  quarter  of  a  pound  of  protein,  the  same  amount  of  fat, 
and  about  one  pound  of  carbohydrate  to  provide  for  the  growth, 
waste,  and  repair  of  the  body  and  the  energy  used  up  in  one  day. 

The  Daily  Calorie  Requirement.  —  Put  in  another  way,  At- 
water's  standard  for  a  man  at  light  exercise  is  food  enough  to 
yield  2816  Calories ;  of  these,  410  Calories  are  from  protein,  930 
Calories  from  fat,  and  1476  Calories  from  carbohydrate.  That  is, 
for  every  100  Calories  furnished  by  the  food,  14  are  from  protein, 
32  from  fat,  and  54  from  carbohydrate.  In  exact  numbers,  the 
day's  ration  as  advocated  by  Atwater  would  contain  about  100 
grams  or  3.7  ounces  protein,  100  grams  or  3.7  ounces  fat,  and  360 
grams  or  13  ounces  carbohydrate.  Professor  Chittenden  of  Yale 
University,  another  food  expert,  thinks  we  need  proteins,  fats,  and 
carbohydrates  in  about  the  proportion  of  1  to  3  to  6,  thus  differing 
from  Atwater  in  giving  less  protein  in  proportion.  Chittenden's 
standard  for  the  same  man  is  food  to  yield  a  total  of  2360  Calories, 
of  which  protein  furnishes  236  Calories,  fat  708  Calories,  and  car- 
bohydrates 1416  Calories.  For  every  100  Calories  furnished  by 
the  food,  10  are  from  protein,  30  from  fat,  60  from  carbohydrate. 
In  actual  amount  the  Chittenden  diet  would  contain  2.16  ounces 
protein,  2.83  ounces  fat,  and  13  ounces  carbohydrate.  A  German 
named  Voit  gives  as  ideal  25  Calories  from  proteins,  20  from 
fat,  and  55  from  carbohydrate,  out  of  every  100  Calories;  this 
is  nearer  our  actual  daily  ration.  In  addition,  an  ounce  of  salt 
and  nearly  one  hundred  ounces  of  water  are  used  in  a  day. 


FOODS   AND   DTETARTER 


29,:^ 


PROTEIN 


FATS  CARBOHYDRATES  FUEL  VALUE 


FOOD 

MATERIALS 


Beef,  round 


Beef,  sirloin 


Beef,  shoulder 


Mutton,  leg 


Pork,  loin 


Pork,  salt,  fat 


Ham,  smoked 


Codfish,  fresh, 
dressed 


Oysters  35  cents 
per  quart 


Milk,  6  cents 
per  quart 


Butter 


Cheese 


Eggs,  24  cents 
per  dozen 


Corn  meal 


Oat  meal 


Beans,  white,  dried 


Rice 


Potatoes,  60  cents 
per  bushel 


Sugar 


Ho 

QjD. 

a. 


14 


20 


12 


16 


12 


12 


18 


10 


18 


25 


16 


16 


5  « 


POUNDS 


.71 


.50 


.83 


.63 


.83 


.83 


.56 


1.00 


.56 


3.33 


.40 


.63 


.63 


2.50 


2.00 


1.25 


10.00 


1.67 


POUNDS  OF  NUTRIENTS  AND  CALORIES  OP  FUEL  VALUE 
IN  10  CENTS  WORTH 


1  LB. 

J 


2  LBS. 


3  LBS. 

_i 


2,000  CAL. 


4.000  CAL. 


6.000  CAL. 


m^ 


y//////////.m'A 


I 


Table  showing  the  cost  of  various  foods.  Using  this  table,  make  up  an  ccunuinical 
dietary  for  one  day,  three  meals,  for  a  man  doing  moderate  work.  Give 
reasons  for  the  amount  of  food  used  and  for  your  choice  of  foods.  Make  up 
another  dietary  in  the  same  manner,  using  expensive  foods.  What  is  the 
difference  in  your  bill  for  the  day  ? 


284  FOODS  AND  DIETARIES 

A  Mixed  Diet  Best.  —  Knowing  the  proportion  of  the  different 
food  substances  required  by  man,  it  will  be  an  easy  matter  to 
determine  from  the  tables  and  charts  shown  you  the  best  foods 
for  use  in  a  mixed  diet.  Meats  contain  too  much  nitrogen  in 
proportion  to  the  other  substances.  In  milk,  the  proportion  of 
])roteins,  carbohydrates,  and  fats  is  nearly  right  to  make  proto- 
plasm ;  a  considerable  amount  of  mineral  matter  being  also  pres- 
ent. For  these  reasons,  milk  is  extensively  used  as  a  food  for 
children,  as  it  combines  food  material  for  the  forming  of  proto- 
plasm with  mineral  matter  for  the  building  of  bone.  Some  vege- 
tables (for  example,  peas  and  beans)  contain  a  large  amount 
of  nitrogenous  material  but  in  a  less  digestible  form  than  is  found 
in  some  other  foods.  Vegetarians,  then,  are  correct  in  theory 
when  they  state  that  a  diet  of  vegetables  may  contain  every- 
thing necessary  to  sustain  life.  But  a  mixed  diet  containing 
meat  is  healthier.  A  purely  vegetable  diet  contains  much  waste 
material,  such  as  the  cellulose  forming  the  walls  of  plant  cells, 
which  is  indigestible.  It  has  been  recently  discovered  that  the 
outer  coats  of  some  grains,  as  rice,  contain  certain  substances 
(enzymes)  which  aid  in  digestion.  In  the  case  of  polished  rice, 
when  this  outer  coat  is  removed  the  grain  has  much  less  food  value. 

Daily  Fuel  Needs  of  the  Body.  —  It  has  been  pointed  out  that 
the  daily  diet  should  differ  widely  according  to  age,  occupation, 
time  of  year,  etc.  The  following  table  shows  the  daily  fuel  needs 
for  several  ages  and  occupations :  — 

Daily   Calorie   Needs   (Approximately) 


1.  For  child  under  2  years 900  Calor 

2.  For  child  from  2-5  years 1200  Calor 

3.  For  child  from  6-9  years 1500  Calor 

4.  For  child  from  10-12  years 1800  Calor 

5.  For  child  from  12-14  (woman,  light  work,  also)       .     .     2100  Calor 

6.  For  boy  (12-14),  girl  (15-16),  man,  sedentary  .     .     .     2400  Calor 

7.  For  boy  (15-16)  (man,  light  muscular  work)     .     .     .     2700  Calor 

8.  For  man,  moderately  active  muscular  work  ....     3000  Calor 

9.  For  farmer  (busy  season) 3200  to  4000  Calor 

10.  For  ditchers,  excavators,  etc 4000  to  5000  Calor 

11.  For  lumbermen,  etc 5000  and  more  Calor 


es 
es 
es 
es 
es 
es 
es 
es 
es 
es 
es 


FOODS   AND   DIETARIES 


285 


Normal  Heat  Output.  —  The  following  table  gives  the  result  of 
some  experiments  made  to  determine  the  hourly  and  daily  expen- 
diture of  energy  ot  the  average  normal  grown  person  when  asleep 
and  awake,  at  Wv^rk  or  at  rest :  — 

Average  Normal   Output   of   Heat   from  the   Body 


Conditions  of  Muscular  Activity 


Man  at  rest,  sleeping 

Man  at  rest,  awake,  sitting  up 

Man  at  light  muscular  exercise         .     .     .     . 
Man  at  moderately  active  muscular  exercise 
Man  at  severe  muscular  exercise      .     .     .     . 
Man  at  very  severe  muscular  exercise       .     . 


Average 

Calories 

PER  Hour 

65  Calories 

100  Calories 

170  Calories 

290  Calories 

450  Calories 

600  Calories 

It  is  very  simple  to  use  such  a  table  in  calculating  the  number 
of  Calories  which  are  spent  in  twenty-four  hours  under  different 
bodily  conditions.  For  example,  suppose  the  case  of  a  clerk  or 
school  teacher  leading  a  relatively  inactive  life,  who 


sleeps  for  9  hours 

works  at  desk  9  hours 

reads,  writes,  or  studies  4  hours     . 
walks  or  does  light  exercise  2  hours 


X    65  Calories  = 

585 

X  100  Calories  = 

900 

X  100  Calories  = 

400 

X  170  Calories  = 

340 

2225 


This  comes  out,  as  we  see,  very  close  to  example  6  of  the  table  ^ 
on  page  284. 

How  we  may  Find  whether  we  are  Eating  a  properly  Balanced 
Diet.  —  We  already  know  approximately  our  daily  Calorie  needs 
and  about  the  proportion  of  protein,  fat,  and  carbohydrate  needed. 
Dr.  Irving  Fisher  of  Yale  University  has  worked  out  a  very  easy 
method  of  determining  whether  one  is  living  on  a  proper  diet.  He 
has  made  up  a  number  of  tables,  in  which  he  has  designated 
portions  of  food,  each  of  which  furnishes  100  Calories  of  energy. 

1  The  above  tables  have  been  taken  from  the  excellent  pamphlet  of  the  Cornell 
Reading  Course,  No.  6,  Human  Nutrition. 


Table  of  100  Calorie  Portions  —  Modified  from  Fisher 


_  ._- . ^_^__-^^— ^—^^^ 

Port,  containing 

Cal. 

Furnished 

Price 

►jr 

a 

. 

Food 

100  Calories 

Wt.  in 
100  Cai 
Port. 

49 

% 
f^ 

1  ^ 

n 

I-H 

ij 
o  . 

§1 

Oysters       .     .     . 

1  doz. 

6.8 

22 

29 

.175 

.07 

Bean  soup       .     . 

1  small  serving 

2.6 

24 

12 

64 

.007 

Cream  of  corn     . 

f  ordin.  serv. 

3.1 

11 

58 

31 

.02 

Vegetable  soup    . 

§  ordin.  serv. 

2.4 

8 

89 

3 

.01 

Cod  fish  (fresh) 

ordin.  serv. 

5 

95 

5 

0 

.12 

.04 

Salmon  (canned) 

small  serv. 

1.75 

45 

55 

0 

.22 

.03 

Chicken      .     .     . 

^  large  serv. 

1.75 

39 

56 

5 

.22 

.05 

Veal  cutlet      .     . 

f  large  serv. 

2.4 

54 

46 

0 

.28 

.045 

Beef,  corned   .     . 

1  large  serv. 

1.0 

15 

85 

0 

.16 

.01 

Beef,  sirloin    .     . 

small  serv. 

1.6 

33 

67 

0 

.34 

.04 

Beef,  round     .     . 

small  serv. 

1.8 

39 

61 

0 

.24 

.025 

Ham,  lean       .     . 

ordin.  serv. 

1.1 

28 

72 

0 

.22 

.015 

Lamb  chops    .     . 

1  ordin.  serv. 

1.0 

24 

76 

0 

.20 

.013 

Mutton,  leg    .     . 

ordin.  serv. 

1.2 

35 

65 

0 

.20 

.015 

Eggs,  boiled    .     . 

1  large  egg 

2.1 

32 

68 

0 

.30  doz. 

.025 

Eggs,  scrambled  . 

1|  ordin.  serv. 

2.5 

37 

58 

5 

.30  doz 

.03 

Beans,  baked  .     . 

side  dish 

2.66 

21 

18 

61 

.08 

.013 

Potatoes,  mashed 

ordin.  serv. 

3.2 

10 

25 

65 

.02 

.005 

Macaroni        .     . 

^  large  serv. 

.95 

15 

3 

82 

.10 

.01 

Potato  salad   .     . 

ordin.  serv. 

2.25 

10 

57 

33 

.20 

.025 

Tomatoes,  sliced 

4  large  serv. 

15. 

15 

16 

69 

.10 

.10 

Rolls,  plain     .     . 

1  large  roll 

1.2 

12 

7 

81 

.10  doz. 

.01 

Butter        .     .     . 

ordin.  pat 

.44 

5 

99.5 

.35 

.01 

Wheat  bread 

1  small  slice 

.96 

15 

5 

80 

.07 

.005 

Chocolate  cake    . 

1  ord.  sq.  piece 

.98 

7 

22 

71 

.32 

.02 

Gingerbread 

^  ord.  sq.  piece 

.96 

6 

23 

71 

.16 

.01 

Custard  pudding 

ordin.  serv. 

3.25 

18 

42 

40 

.15 

.03 

Rice  pudding  .     . 

very  small  serv. 

2.65 

8 

13 

79 

.13 

.02 

Apple  pie        .     . 

I  piece 

1.3 

5 

32 

63 

.013 

Cheese,  American 

1|  cu.  in. 

.77 

25 

73 

2 

.19 

.01 

Crackers  (soda)  . 

2  crackers 

.9 

10 

20 

70 

.10 

.007 

Currant  jelly  .     . 

2  heap,  spoons 

1.1 

2 

0 

98 

.40 

.025 

Sugar     .... 

3  teaspoons 

.86 

0 

0 

100 

.06 

.003 

Milk  as  bought   . 

small  glass 

4.9 

19 

52 

29 

.05 

.015 

Milk,  cond.,  sweet 

4  teaspoons 

1.06 

10 

23 

67 

.01 

Oranges      .     .     . 

1  large  one 

9.4 

6 

3 

91 

.025 

Peanuts      .     .     . 

13  double  ones 

.62 

20 

63 

17 

.004 

Almonds,  shelled 

8-15 

.53 

13 

77 

10 

.025 

286 


FOODS   AND   DIETARIES  287 

The  tables  show  the  proportion  of  protein,  fat,  and  carbohydrate 
in  each  food,  so  that  it  is  a  simple  matter  by  using  such  a  table 
to  estimate  the  proportions  of  the  various  nutrients  in  our  dietary. 
We  may  depend  upon  taking  somewhere  near  the  proper  amount 
of  food  if  we  take  a  diet  based  upon  either  Atwater's,  Chittenden's, 
or  Voit's  standard.  One  of  the  most  interesting  and  useful 
pieces  of  home  work  that  you  can  do  is  to  estimate  your  own 
personal  dietary,  using  the  tables  giving  the  100-Calorie  portion 
to  see  if  you  have  a  properly  balanced  diet.  From  the  table  on 
page  286  make  out  a  simple  dietary  for  yourself  for  one  day, 
estimating  your  own  needs  in  Calories  and  then  picking  out  100- 
Calorie  portions  of  food  which  will  give  you  the  proper  propor- 
tions of  protein,  fat,  and  carbohydrate. 

From  the  preceding  table  plan  a  well-balanced  and  cheap  dietary 
for  one  day  for  a  family  of  five,  two  adults  and  three  children. 
Make  a  second  dietary  for  the  same  time  and  same  number  of 
people  which  shall  give  approximately  the  same  amount  of  tissue 
and  energy  producing  food  from  more  expensive  materials. 

Food  Waste  in  the  Kitchen.  —  Much  loss  occurs  in  the  im- 
proper cooking  of  foods.  Meats  especially,  when  overdone, 
lose  much  of  their  flavor  and  are  far  less  easily  digested  than  when 
they  are  cooked  rare.  The  chief  reasons  for  cooking  meats  are 
that  the  muscle  fibers  may  be  loosened  and  softened,  and  that  the 
bacteria  or  other  parasites  in  the  meat  may  be  killed  by  the  heat. 
The  common  method  of  frying  makes  foods  less  digestible.  Stew- 
ing is  an  economical  as  well  as  healthful  method.  A  good  way  to 
prepare  meat,  either  for  stew  or  soup,  is  to  place  the  meat,  cut  in 
small  pieces,  in  cold  water,  and  allow  it  to  simmer  for  several 
hours.  Rapid  boiling  toughens  the  muscle  fibers  by  the  too  rapid 
coagulation  of  the  albuminous  matter  in  them,  just  as  the  white 
of  egg  becomes  tough  when  boiled  too  long.  Boiling  and  roasting 
are  excellent  methods  of  cooking  meat.  In  order  to  prevent  the 
loss  of  the  nutrients  in  roasting,  it  is  well  to  baste  the  meat  fre- 
quently ;  thus  a  crust  is  formed  on  the  outer  surface  of  the  meat, 
which  prevents  the  escape  of  the  juices  from  the  inside. 

Vegetables  are  cooked  in  order  that  the  cells  containing  starch 
grains  may  be  burst  open,  thus  allowing  the  starch  to  be  more 


288  FOODS   AND   DIETARIES 

easily  attacked  by  the  digestive  fluids.  Inasmuch  as  water  may 
dissolve  out  nutrients  from  vegetable  tissues,  it  is  best  to  boil 
them  rapidly  in  a  small  amount  of  water.  This  gives  less  time 
for  the  solvent  action  to  take  place.  Vegetables  should  be  cooked 
with  the  outer  skin  left  on  when  it  is  possible. 

Adulterations  in  Foods.  —  The  addition  of  some  cheaper  sub- 
stance to  a  food,  or  the  subtraction  of  some  valuable  substance 
from  a  food,  with  the  view  to  cheating  the  purchaser,  is  known 
as  adulteration.  Many  foods  which  are  artificially  manufactured 
have  been  adulterated  to  such  an  extent  as  to  be  almost  unfit  for 
food,  or  even  harmful.  One  of  the  commonest  adulterations  is  the 
substitution  of  grape  sugar  (glucose)  for  cane  sugar.  Glucose, 
however,  is  not  a  harmful  adulterant.  It  is  used  largely  in  candj^' 
making.  Flour  and  other  cereal  foods  are  sometimes  adulterated 
with  some  cheap  substitutes,  as  bran  or  sawdust.  Alum  is  some- 
times added  to  make  flour  whiter.  Probably  the  food  which  suffers 
most  from  adulteration  is  milk,  as  water  can  be  added  without 
the  average  person  being  the  wiser.  By  means  of  an  inexpensive 
instrument  known  as  a  lactometer,  this  cheat  may  easily  be  de- 
tected. In  most  cities,  the  milk  supply  is  carefully  safeguarded, 
because  of  the  danger  of  spreading  typhoid  fever  from  impure 
milk  (see  Chapter  XX) .  Before  the  pure  food  law  was  passed  in 
1906,  milk  was  frequently  adulterated  with  substances  like  for- 
malin to  make  it  keep  sweet  longer.  Such  preservatives  are 
harmful,  and  it  is  now  against  the  law  to  add  anything  whatever 
to  milk. 

Coffee,  cocoa,  and  spices  are  subject  to  great  adulteration; 
cottonseed  oil  is  often  substituted  for  olive  oil ;  butter  is  too 
frequently  artificial ;  while  honey,  sirups  of  various  kinds,  cider 
and  vinegar,  have  all  been  found  to  be  either  artificially  made  from 
cheaper  substitutes  or  to  contain  such  substitutes. 

Pure  Food  Laws.  —  Thanks  to  the  National  Pure  Food  and 
Drug  Law  passed  by  Congress  in  1906,  and  to  the  activity  of 
various  city  and  state  boards  of  health,  the  opportunity  to  pass 
adulterated  foods  on  the  public  is  greatly  lessened.  This  law 
compels  manufacturers  of  foods  or  medicines  to  state  the  compo- 
sition of  their  products  on  the  labels  placed  on  the  jars  or  bottles. 


FOODS   AND   DIETARIES  289 

So  if  a  person  reads  the  label  he  can  determine  exactly  what  lie 
is  getting  for  his  money. 

Impure  Water.  —  Great  danger  comes  from  drinking  impure 
water.  This  subject  has  already  been  discussed  under  Bacteria, 
where  it  was  seen  that  the  spread  of  typhoid  fever  in  particular  is 
due  to  a  contaminated  water  supply.  As  citizens,  we  must  aid  all 
legislation  that  will  safeguard  the  water  used  by  our  towns  and 
cities.  Boiling  water  for  ten  minutes  or  longer  will  render  it 
safe  from  all  organic  impurities. 

Stimulants.  —  We  have  learned  that  food  is  anything  that 
supplies  building  material  or  releases  energy  in  the  body;  but 
some  materials  used  by  man,  presumably  as  food,  do  not  come 
under  this  head.  Such  are  tea  and  coffee.  When  taken  in 
moderate  quantities,  they  produce  a  temporary  increase  in  the 
vital  activities  of  the  person  taking  them.  This  is  said  to  be  a 
stimulation ;  and  material  taken  into  the  digestive  tract,  produc- 
ing this,  is  called  a  stimulant.  In  moderation,  tea  and  coffee 
appear  to  be  harmless.  Some  people,  however,  cannot  use  either 
without  ill  effects,  even  in  small  quantity.  It  is  the  habit  formed 
of  relying  upon  the  stimulus  given  by  tea  or  coffee  that  makes 
them  a  danger  to  man.  Cocoa  and  chocolate,  although  l^oth 
contain  a  stimulant,  are  in  addition  good  foods,  having  from  12 
per  cent  to  21  per  cent  of  protein,  from  29  per  cent  to  48  per  cent 
fat,  and  over  30  per  cent  carbohydrate  in  their  composition. 

Is  Alcohol  a  Food? — ^  The  question  of  the  use  of  alcohol  has 
been  of  late  years  a  matter  of  absorbing  interest  and  im{:)ortance 
among  physiologists.  A  few  years  ago  Dr.  Atwater  performed  a 
series  of  very  careful  experiments  by  means  of  the  resi3iration 
calorimeter,  to  ascertain  whether  alcohol  is  of  use  to  the  body  as 
food.i  In  these  experiments  the  subjects  were  given,  instead  of 
their  daily  allotment  of  carbohydrates  and  fats,  enough  alcohol 
to  supply  the  same  amount  of  energy  that  these  foods  would 
have  given.  The  amount  was  calculated  to  be  about  two  and 
one  half  ounces  per  day,  about  as  much  as  would  be  contained  in 

1  Alcohol  is  made  up  of  carbon,  oxygen,  and  hydrogen.      It  is  verj'  easily  oxidized, 
but  it  cannot,  as  is  shown  by  the  chemical  formula,  be  of  use  to  the  body  in  tissue 
building,  because  of  its  lack  of  nitrogen. 
HX7NTER,   CIV.   BI. 19 


290  FOODS  AND   DIETARIES 

a  bottle  of  light  wine.^  This  alcohol  was  administered  in  small 
doses  six  times  during  the  day.  Professor  Atwater's  results  may 
be  summed  up  briefly  as  follows :  — 

1.  The  alcohol  administered  was  almost  all  oxidized  in  the  body. 

2.  The  potential  energy  in  the  alcohol  was  transformed  into  heat 
or  muscular  work. 

3.  The  body  did  about  as  well  with  the  rations  including  alco- 
hol as  it  did  without  it. 

The  committee  of  fifty  eminent  men  appointed  to  report  on  the 
physiological  aspects  of  the  drink  problem  reported  that  a  large 
number  of  scientific  men  state  that  they  are  in  the  habit  of  taking 
alcoholic  liquor  in  small  quantities,  and  many  report  that  they  do 
not  feel  harm  thereby.  A  number  of  scientists  seem  to  agree 
that  within  limits  alcohol  may  be  a  kind  of  food,  although  a  very 
poor  food. 

On  the  other  hand,  we  know  that  although  alcohol  may  techni- 
cally be  considered  as  a  food,  it  is  a  very  unsatisfactory  food  and, 
as  the  follo\ving  statements  show,  it  has  an  effect  on  the  body 
tissues  which  foods  do  not  have. 

Professor  Chittenden  of  Yale  College,  in  discussing  the  food 
problem  of  alcohol,  writes  as  follows:  "  It  is  true  that  alcohol 
in  moderate  quantities  may  serve  as  a  food,  i.e.  it  can  be  oxidized 
with  the  liberation  of  heat.  It  may  to  some  extent  take  the 
place  of  fat  and  carbohydrates,  but  it  is  not  a  perfect  substitute 
for  them,  and  for  this  reason  alcohol  has  an  action  that  can- 
not be  ignored.  It  reduces  liver  oxidation.  It  therefore  pre- 
sents a  dangerous  side  wholly  wanting  in  carbohydrates  and  fat. 
The  latter  are  simply  burned  up  to  carbonic  acid  and  water  or  are 
transformed  to  glycogen  and  fat,  but  alcohol,  although  more  easily 
oxidized,  is  at  all  times  liable  to  obstruct,  in  a  measure  at  least,  the 
oxidative  processes  of  the  liver  and  probably  of  other  tissues  also, 
thereby  throwing  into  the  circulation  bodies,  such  as  uric  acid, 
which  are  harmful  to  health,  a  fact  which  at  once  tends  to  draw  a 
distinct  line  of  demarcation  between  alcohol  and  the  two  non- 

1  Alcoholic  beverages  contain  the  following  proportions  of  alcohol :  beer,  from 
2  to  5  per  cent ;  wine,  from  10  to  20  per  cent ;  liquors,  from  30  to  70  per  cent.  Pat- 
ent medicines  frequently  contain  as  high  as  60  per  cent  alcohol.     (See  page  294.) 


FOODS  AND   DIETARIES  291 

nitrogenous  foods,  fat  and  carbohydrates.  Another  matter  must 
be  emphasized,  and  it  is  that  the  form  in  which  alcohol  is  taken  is 
of  importance.  Port  wine,  for  instance,  has  more  influence  on  the 
amount  of  uric  acid  secreted  than  an  equivalent  amount  of  alcohol 
has  in  some  other  form.  To  conclude  :  as  an  adjunct  to  the  ordi- 
nary daily  diet  of  the  healthy  man  alcohol  cannot  be  considered 
as  playing  the  part  of  a  true  nonnitrogenous  food."  —  Quoted  in 
American  Journal  of  Inebriety,  Winter,  1906. 

Effect  of  Alcohol  on  Living  Matter.  —  If  we  examine  raw  white 
of  egg,  we  find  a  protein  which  closely  resembles  protoplasm  in 
its  chemical  composition;  it  is  called  albumen.  Add  to  a  little 
albumen  in  a  test  tube  some  95  per  cent  alcohol  and  notice  what 
happens.  As  soon  as  the  alcohol  touches  the  albumen  the  latter 
coagulates  and  becomes  hard  like  boiled  white  of  egg.  Shake  the 
alcohol  with  the  albumen  and  the  entire  mass  soon  becomes  a 
solid.  This  is  because  the  alcohol  draws  the  water  out  of  the 
albumen.  It  has  been  shown  that  albumen  is  somewhat  like 
protoplasm  in  structure  and  chemical  composition.  Strong  al- 
cohol acts  in  a  similar  manner  on  living  matter  when  it  is  ab- 
sorbed by  the  living  body  cells.  It  draws  water  from  them  and 
hardens  them.  It  has  a  chemical  and  physical  action  upon  living 
matter. 

Alcohol  a  Poison.  —  But  alcohol  is  also  in  certain  quantities  a 
poison.  A  commonly  accepted  definition  of  a  poison  is  that  it  is 
any  substance  which,  when  taken  into  the  body,  tends  to  cause 
serious  detriment  to  health,  ox  the  death  of  the  organism.  That 
alcohol  may  do  this  is  well  known  by  scientists. 

It  is  a  matter  of  common  knowledge  that  alcohol  taken  in  small 
quantities  does  not  do  any  apparent  harm.  But  if  we  examine  the 
vital  records  of  life  insurance  companies,  we  find  a  large  number  of 
deaths  directly  due  to  alcohol  and  a  still  greater  number  due  in 
part  to  its  use.  In  the  United  States  every  year  there  are  a  third 
more  deaths  from  alcoholism  and  cirrhosis  of  the  liver  (a  disease 
directly  caused  by  alcohol)  than  there  are  from  tAqihoid  fever.  The 
poisonous  effect  is  not  found  in  small  doses,  but  it  ultimately  shows 
its  harmful  effect.  Hardening  of  the  arteries,  an  old-age  disease, 
is  rapidly  becoming  in  this  country  a  disease  of  the  middle  aged. 


292 


FOODS  AND   DIETARIES 


From  it  there  is  no  escape.  It  is  chiefly  caused  by  the  cumulative 
effect  of  alcohol.  The  diagram  following,  compiled  by  two  English 
life    insurance    companies   that    insure    moderate  drinkers    and 


Companies 


100  EXPECTED    DEATHS 


Sceptre 

Life  Insurance 

Cornparo) 
1884^1909. 


MODERATE       DRINKERS 


ABSTAINERS 


79.7 
I 


United  Kvn^doYYi 
Temperance  ^'^^ 

General  Provldertt 

Irtstitution 
1866-1909. 


MODERATE    DRINKERS 


ABSTAINERS 


|93| 

J' 
7D, 


Abstainers  live  longer  than  moderate  drinkers. 

abstainers,  shows  the  death  rate  to  be  considerably  higher  among 
those  who  use  alcohol. 

Dr.  Kellogg,  the  founder  of  the  famous  Battle  Creek  Sanitarium, 
points  out  that  strychnine,  quinine,  and  many  other  drugs  are 
oxidized  in  the  body  but  surely  cannot  be  called  foods.  The 
following  reasons  for  not  considering  alcohol  a  food  are  taken 
from  his  writings  :  — 

''  1.  A  habitual  user  of  alcohol  has  an  intense  craving  for  his 
accustomed  dram.  Without  it  he  is  entirely  unfitted  for  business. 
One  never  experiences  such  an  insane  craving  for  bread,  potatoes, 
or  any  other  particular  article  of  food. 

"2.  By  continuous  use  the  body  acquires  a  tolerance  for 
alcohol.  That  is,  the  amount  which  may  be  imbibed  and  the 
amount  required  to 'produce  the  characteristic  effects  first  expe- 
rienced gradually  increase  until  very  great  quantities  are  some- 
times required  to  satisfy  the  craving  which  its  habitual  use  often 
produces.  This  is  never  the  case  with  true  foods.  .  .  .  Alcohol 
behaves  in  this  regard  just  as  does  opium  or  any  other  drug.  It 
has  no  resemblance  to  a  food. 


FOODS   AND   DIETARIES 


293 


"  3.  When  alcohol  is  withdrawn  from  a  person  who  has  been 
accustomed  to  its  daily  use,  most  distressing  effects  are  expe- 
rienced. .  .  .  Who  ever  saw  a  man's  hand  tromi)ling  or  his 
nervous  system  unstrung  because  he  could  not  get  a  potato  or  a 
piece  of  cornbread  for  breakfast?  In  this  respect,  also,  alcohol 
behaves  like  opium,  cocaine,  or  any  other  enslaving  drug. 

"  4.  Alcohol  lessens  the  appreciation  and  the  value  of  brain  and 
nerve  activity,  while  food  reenforces  nervous  and  mental  energy. 

"  5.  Alcohol  as  a  protoplasmic  poison  lessens  muscular  pow(.'r, 
whereas  food  increases  energy  and  endurance. 

"  6.  Alcohol  lessens  the  power  to  endure  cold.  This  is  true  to 
such  a  marked  degree  that  its  use  by  persons  accompanying  Arctic 
expeditions  is  absolutely  prohibited.  Food,  on  the  other  hand, 
increases  ability  to  endure  cold.  The  temperature  after  taking 
food  is  raised.  After  taking  alcohol,  the  temperature,  as  shown  by 
the  thermometer,  is  lowered. 

"7.  Alcohol  cannot  be  stored  in  the  body  for  future  use,  whereas 
all  food  substances  can  be  so  stored. 

"  8.  Food  burns  slowly  in  the  body,  as  it  is  required  to  satisfy 
the  body's  needs.  Alcohol  is  readily  oxidized  and  eliminated,  the 
same  as  any  other  oxidizable  drug." 

The  Use  of  Tobacco.  —  A  well-known  authority  defines  a  nar- 
cotic as  a  substance  "  which  directly  induces  sleep,  blunts  the  senses, 
and,  in  large  amounts,  produces  complete 
insensibility. ''  Tobacco,  opium,  chloral, 
and  cocaine  are  examples  of  narcotics. 
Tobacco  owes  its  narcotic  influence  to 
a  strong  poison  known  as  nicotine.  Its 
use  in  killing  insect  parasites  on  plants 
is  well  known.  In  experiments  with 
jellyfish  and  other  lowly  organized 
animals,  the  author  has  found  as  small 
a  per  cent  as  one  part  of  nicotine  to 
one  hundred  thousand  parts  of  sea 
water  to  be  sufficient  to  profoundly 
affect  an  animal  placed  within  it. 
The  illustration  here  given  shows  the 


Experiment  (by  Davison)  to 
show  how  the  nicotine  in  six 
cigarettes  was  sufficitMit  to  kill 
this  fish.  The  smoke  from 
the  cigarettes  was  passed 
through  the  water  in  which 
the  fish  is  swimming. 


294 


FOODS   AND   DIETARIES 


effect  of  nicotine  upon  a  fish,  one  of  the  vertebrate  animals. 
Nicotine  in  a  pure  form  is  so  powerful  a  poison  that  two  or  three 
drops  would  be  sufficient  to  cause  the  death  of  a  man  by  its 
action  upon  the  nervous  system,  especially  the  nerves  controlling 
the  beating  of  the  heart.  This  action  is  well  known  among  boys 
training  for  athletic  contests.  The  heart  is  affected ;  boys  become 
^'  short-winded  "  as  a  result  of  the  action  on  the  heart.  It  has 
been  demonstrated  that  tobacco  has,  too,  an  important  effect  on 
muscular  development.  The  stunted  appearance  of  the  young 
smoker  is  well  known. 

Use  and  Abuse  of  Drugs.  —  The  American  people  are  addicted 
to  the  use  of  drugs,  and  especially  patent  medicines.     A  glance  at 


The  amounts  of  alcohol  in  some  liquors  and  in  some  patent  medicines. 
a,  beer,  5  %  ;  b,  claret,  8  %  ;  c,  champagne,  9  %  ;  d,  whisky,  50  %  ; 
e,  well-known  sarsaparilla,  18  %  ;  /,  g,  h,  much-advertised  nerve  tonics, 
20  %,  21  %,  25  %  ;  i,  another  much-advertised  sarsaparilla,  27  %; 
y,  a  well-known  tonic,  28  %  ;  k,  I,  bitters,  37  %,  44  %  alcohol. 


the  street-car  advertisements  shows  this.  Most  of  the  medicines 
advertised  contain  alcohol  in  greater  quantity  than  beer  or  wine, 
and  many  of  them  have  opium,  morphine,  or  cocaine  in  their 
composition.  Paregoric  and  laudanum,  medicines  sometimes  given 
to  young  children,  are  examples  of  dangerous  drugs  that  contain 
opium.     Dr.    George    D.    Haggard    of    Minneapohs   has   shown 


FOODS   AND   DIETARIES  295 

by  many  analyses  that  a  large  number  of  the  so-called  "  malts," 
"  malt  extracts,"  and  "  tonics,"  including  several  of  the  best  known 
and  most  advertised  on  the  market,  are  simply  disguised  beers 
and,  frequently,  very  poor  beers  at  that.  These  drugs,  in  addition 
to  being  harmful,  affect  the  person  using  them  in  such  a  manner 
that  he  soon  feels  the  need  for  the  drug.  Thus  the  drug  habit  is 
formed,  —  a  condition  which  has  wrecked  thousands  of  lives.  A 
number  of  articles  on  patent  medicines  recently  appeared  in  a 
leading  magazine  and  have  been  collected  and  published  under  the 
title  of  The  Great  American  Fraud.  In  this  booklet  the  author 
points  out  a  number  of  different  kinds  of  ''  cures  "  and  patent 
medicines.  The  most  dangerous  are  those  headache  or  neuralgia 
cures  containing  acetanilid.  This  drug  is  a  heart  depresser  and 
should  not  be  used  without  medical  advice.  Another  drug  which 
is  responsible  for  habit  formation  is  cocaine.  This  is  often  found  in 
catarrh  or  other  cures.  Alcohol  is  the  basis  of  all  tonics  or 
"  bracers."  Every  boy  and  girl  should  read  this  booklet  so  as  to 
be  forearmed  against  evils  of  the  sort  just  described. 

Reference  Reading  on  Foods 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 

Allen,  Civics  and  Health.     Ginn  and  Company. 

Bulletin  13,  American  School  of  Home  Economics,  Chicago. 

Cornell  University  Reading  Course,  Buls.  6  and  7,  Human  Nutrition. 

Davison,  The  Human  Body  and  Health.     American  Book  Company. 

Jordan,  The  Principles  of  Human  Nutrition.     The  Macmillan  Company. 

Kebler,  L.  F.,  Habit-forming  Agents.     Farmers'  Bulletin  393,  U.S.  Dept.  of  Agri. 

Lusk,  Science  and  Nutrition.     W.  B.  Saunders  Company. 

Norton,  Foods  and  Dietetics.     American  School  of  Home  Economics. 

Olsen,  Pure  Foods.     Ginn  and  Company. 

Sharpe,  A  Laboratory  Manual  for  the  Solution  of  Problems  in  Biology,  pp.  226-240. 

American  Book  Company. 
Stiles,  Nutritional  Physiology.     W.  B.  Saunders  Company. 
The  Great  American  Fraud.     American  Medical  Association,  Chicago. 
The  Propaganda  for  Reform  in  Proprietary  Medicines.     Am.  Medical  Association. 
Farmers'  Bulletin:    numbers  23,  34,  42,  85,  93,  121,  128,  132,  142,  182,  249,  295. 

298. 
Reprint  from  Yearbook,  1901,  Atwater,  Dietaries  in  Public  InstitutioJis. 
Reprint  from  Yearbook,  1902,  Milner,  Cost  of  Food  related  to  its  Nutritive  Vaho 
Experiment  Station,  Circular  46,  Langworthy,  Functions  and  Uses  of  Food. 


XX.    DIGESTION  AND  ABSORPTION 

Problems,  —  To  determine  where  digestion  takes  place  hy  ex- 
amining :  — 
ia)  The  functions  of  glands. 

(b)  The  ivorh  done  in  the  mouth. 

(c)  The  worJc  done  in  the  stomach. 

id)  The  ivorh  done  in  the  small  intestine. 

ie)    The  function  of  the  liver. 

To  discover  the  absorbing  apparatus  and  how  it  is  used. 

Laboratory  Suggestions 

Demonstration  of  food  tube  of  man  (manikin).  —  Comparison  with  food 
tube  of  frog.  Drawing  (comparative)  of  food  tube  and  digestive  glands 
of  frog  and  man. 

Demonstration  of  simple  gland.  —  (Microscopic  preparation.) 

Home  experiment  and  laboratory  demonstration.  —  The  digestion  of 
starch  by  saliva.     Conditions  favorable  and  unfavorable. 

Demonstration  experiment,  —  The  digestion  of  proteins  with  artificial 
gastric  juice.     Conditions  favorable  and  unfavorable. 

Demonstration.  —  An  emulsion  as  seen  under  the  compound  microscope. 

Demonstration.  —  Emulsification  of  fats  with  artificial  pancreatic  fluid. 
Digestion  of  starch  and  protein  with  artificial  pancreatic  fluid. 

Demonstration  of  "tripe"  to  show  increase  of  surface  of  digestive  tube. 

Laboratory  or  home  exercise.  —  Make  a  table  shoA\dng  the  changes  pro- 
duced upon  food  substances  by  each  digestive  fluid,  the  reaction  (acid  or 
alkaline)  of  the  fluid,  when  the  fluid  acts,  and  what  results  from  its  action. 

Purpose  of  Digestion.  —  We  have  learned  that  starch  and  pro- 
tein food  of  plants  are  formed  in  the  leaves.  A  plant,  however,  is 
unable  to  make  use  of  the  food  in  this  condition.  Before  it  can 
be  transported  from  one  part  of  the  plant  body  to  another,  it  is 
changed  into  a  soluble  form.  In  this  state  it  can  be  passed  from 
cell  to  cell  by  the  process  of  osmosis.  Much  the  same  condition 
exists  in  animals.  In  order  that  food  may  be  of  use  to  man,  it  must 
be  changed  into  a  state  that  will  allow  of  its  passage  in  a  soluble 
form  through  the  walls  of  the  alimentary  canal,  or  food  tube, 

296 


DIGESTION  AND  ABSORPTION 


297 


This  is  done  by  the  enzymes  which  cause  digestion.  It  will  be  the 
purpose  of  this  chapter  to  discover  where  and  how  digestion  takes 
place  in  our  own  body. 

Alimentary  Canal.  —  In  all  vertebrate  animals,  including 
man,  food  is  taken  in  the  mouth  and  passed  through  a  food  tube 
in  which  it  is  digested.  This  tube  is  composed  of  different  por- 
tions,   named,   respec-  q  « 

tively,  as  we  pass  from 
the  mouth  downward, 
the  gullet,  stomach, 
small  and  large  intes- 
tine, and  rectum. 

Comparison  of  Food 
Tube  of  a  Frog  and 
Man.  —  If  we  compare 
the  food  tube  of  a  dis- 
sected frog  with  the 
food  tube  of  man  (as 
shown  by  a  manikin  or 
chart),  we  find  part  for 
part  they  are  much  the 
same.  But  we  notice 
that  the  intestines  of 
man,  both  small  and 
large,  are  relatively 
longer  than  in  the  frog. 
We  also  notice  in  man  the  body  cavity  or  space  in  which  the 
internal  organs  rest  is  divided  in  two  parts  by  a  wall  of  muscle, 
the  diaphragm,  which  separates  the  heart  and  lungs  from  the 
other  internal  organs.  In  the  frog  no  muscular  diaphragm  exists. 
In  the  frog  we  can  see  plainly  the  silvery  transparent  mesenkry 
or  double  fold  of  the  lining  of  the  body  cavity  in  which  the  organs 
of  digestion  are  suspended.  Numerous  blood  vessels  can  be  found 
especially  in  the  walls  of  the  food  tube. 

Glands.  —  In  addition  to  the  alimentary  canal  projicr,  wo  find  a 
number  of  digestive  glands,  varying  in  size  and  position,  connected 
with  the  canal. 


FROG 


MAN 


The  digestive  tract  of  the  frog  and  man.  Gul,  gullet ; 
S,  stomach;  L,  liver;  G,  gall  bladder;  P,  pancreas; 
Sp,  spleen ;  SI,  small  intestine ;  LI,  large  in- 
testine;   V,  appendix;  .-1,  anus. 


298 


DIGESTION  AND  ABSORPTION 


What  a  Gland  Does.  Enzymes.  —  In  man  there  are  the  saliva 
gland  of  the  mouth,  the  gastric  glands  of  the  stomach,  the  pancreas 
and  liver,  the  two  latter  connected  with  the  small  intestine,  and  the 
intestinal  glands  in  the  walls  of  the  intestine.  Besides  glands  which 
aid  in  digestion  there  are  several  others  of  which  we  will  speak 
later.     As  we  have  already  learned,  a  gland  is  a  collection  of  cells 

which    takes    up    material 
/ood  tube  from  within  the  body  and 

manufactures  from  it  some- 
thing which  is  later  poured 
out  as  a  secretion.  An 
example  of  a  gland  in  plants 
is  found  in  the  nectar- 
secreting  cells  of  a  flower. 

Certain  substances, 
called  enzymes,  formed  by 
glands  cause  the  digestion 
of  food.  The  enzymes 
secreted  by  the  cells  of  the 
glands  and  poured  out  into 
the  food  tube  act  upon 
insoluble  foods  so  as  to 
change  them  to  a  soluble 
form.  The}^  are  the  prod- 
uct of  the  activity  of  the 
cell,  although  they  are  not 
themselves  alive.  We  do 
not  know  much  about 
enzymes  themselves,  but 
we  can  observe  what  they 
do.  Some  enzymes  render  soluble  different  foods,  others  work 
in  the  blood,  still  others  prol)ably  act  within  any  cell  of  the  body 
as  an  aid  to  oxidation,  when  work  is  done.  Enzymes  are  very 
sensitive  to  changes  in  temperature  and  to  the  degree  of  acidity  or 
alkalinity  ^  of  the  material  in  which  they  act.  We  will  find  that 
the  enzymes  found  in  glands  in  the  mouth  will  not  act  long  in  the 
1  The  teacher  should  explain  the  meaning  of  these  terms. 


Diagram  of  a  gland.  i,  the  common  tube 
which  carries  ofif  the  secretions  formed  in 
the  cells  lining  the  cavity  c ;  o,  arteries 
carrying  blood  to  the  glands ;  v,  veins 
taking  blood  away  from  the  glands. 


DIGESTION  AND   ABSORPTION  299 

stomach  because  of  the  change  from  an  alkahne  surrounding  in  the 
mouth  to  that  of  an  acid  in  the  stomach.  Enzj^mes  seem  to  be 
able  to  work  indefinitely,  providing  the  surroundings  are  favorable. 
A  small  amount  of  digestive  fluid,  if  it  liad  Icjng  enough  to  work, 
could  therefore  digest  an  indefinite  amount  of  food. 

Gland  Structure.  —  The  entire  inner  surface  of  the  food  tube 
is  covered  with  a  soft  lining  of  muams  membrane.  This  is  always 
moist  because  certain  cells,  called  mucus  cells,  empty  out  their 
contents  into  the  food  tube,  thus  lubricating  its  inner  surface. 
When  a  large  number  of  cells  which  have  the  power  to  secrete 
fluids  are  collected  together,  the  surface  of  the  food  tube  may  be- 
come indented  at  this  point  to  form  a  pitlike  gland.  Often  such 
depressions  are  branched,  thus  giving  a  greater  secreting  surface, 
as  is  seen  in  the  figure  on  page  298.  The  cells  of  the  gland  are 
alwaj^s  supplied  with  blood  vessels  and  nerves,  for  the  secretions 
of  the  glands  are  under  the  control  of  the  nervous  system. 

How  a  Gland  Secretes.  —  We  must  therefore  imagine  that  as  the 
blood  goes  to  the  cells  of  a  gland  it  there  loses  some  substances 
which  the  gland  cells  take  out  and  make  over  into  the  particular 
enzyme  that  they  are  called  upon  to  manufacture.  Under  certain 
conditions,  such  as  the  sight  or  smell  of  food,  or  even  the  desire 
for  it,  the  activity  of  the  gland  is  stimulated.  It  then  pours  out 
its  secretion  containing  the  digestive  enzyme.  Thus  a  gland  does 
its  work. 

Salivary  Glands.  —  We  are  all  familiar  with  the  substance 
called  saliva  which  acts  as  a  lubricant  in  the  mouth.  Saliva  is 
manufactured  in  the  cells  of  three  pairs  of  glands  wliich  emj^ty 
into  the  mouth,  and  which  are  called,  according  to  their  position, 
the  parotid  (beside  the  ear),  the  suhmaxillary  (under  the  iawbone), 
and  the  sublingual  (under  the  tongue) . 

Digestion  of  Starch.  —  If  we  collect  some  saliva  in  a  test  tube, 
add  to  it  a  little  starch  paste,  place  the  tube  containing  the  mixture 
for  a  few  minutes  in  tepid  water,  and  then  test  with  Fehling's 
solution,  we  shall  find  grape  sugar  present.  Careful  tests  of  the 
starch  paste  and  of  the  saliva  made  separately  will  usually  show 
no  grape  sugar  in  either. 

If  another  test  be  made  for  grape  sugar,  in  a  test  tube  containing 


300 


DIGESTION  AND  ABSORPTION 


starch  paste,  saliva,  and  a  few 
drops  of  any  weak  acid,  the  starch 
will  be  found  not  to  have  changed. 
The  digestion  or  change  of  starch 
to  grape  sugar  is  caused  by  the 
presence  in  the  sahva  of  an  enzyme, 
or  digestive  ferment.  You  will  re- 
member that  starch  in  the  grow- 
ing corn  grain  was  changed  to 
grape  sugar  by  an  enzyme  called 
diastase.  Here  a  similar  action  is 
caused  by  an  enzyme  called  ptyalin. 
_      .  ,      .  .     .   This  ferment  acts  only  in  an  alka- 

Expenment  showing  non-osmosis  ot 

starch  in  tube  A,  and  osmosis  of   line  medium,  at  about  the  tempera- 
sugar  in  tube  B.  |yj.g  Qf  ^ijg  ]30(jy^ 


Mouth  Cavity  in  Man. — 
In  our  study  of  a  frog  we 
find  that  the  mouth  cavity 
has  two  unpaired  and  four 
paired  tubes  leading  from 
it.  These  are  (a)  the  gullet 
or  food  tube,  (b)  the  wind- 
pipe (in  the  frog  opening 
through  the  glottis),  (c)  the 
paired  nostril  holes  {pos- 
terior nares),  (d)  the  paired 
Eustachian  tubes,  leading  to 
the  ear.  All  of  these  open- 
ings are  found  in  man. 

In  man  the  mouth  cavity, 
and  all  internal  surfaces  of 
the  food  tube,  are  lined 
with  a  mucous  membrane. 
The  mucus  secreted  from 
gland  cells  in  this  lining 
makes  a  slippery  surface  so 


The  mouth  cavity  of  man.  e,  Eustachian 
tube ;  hp,  hard  palate ;  sp,  soft  palate ; 
ut,  upper  teeth  ;  be,  buccal  cavity ;  It,  lower 
teeth  ;  t,  tongue  ;  ph,  pharynx  ;  ep,  epiglot- 
tis ;  Ix,  voice  box ;  oe,  gullet ;  tr,  trachea. 


DIGESTION   AND   ABSORPTION 


301 


that  the  food  may  slip  down  easily.  The  roof  of  the  mouth  is 
formed  in  front  by  a  plate  of  bone  called  the  hard  palate,  and  a 
softer  continuation  to  the  back  of  the  mouth,  the  soft  palate.  These 
separate  the  nose  cavity  from  that  of  tlu;  mouth  proper.  The  part 
of  the  space  back  of  the  soft  palate  is  called  the  pharynx,  or  throat 
cavity.  From  the  pharynx  lead  off  the  gullet  and  windpipe, 
the  former  back  of  the  latter.  The  lower  part  of  the  mouth 
cavity  is  occupied  by  a  muscular  tongue.  Examination  of  its 
surface  with  a  looking-glass  shows  it  to  be  almost  covered  in  places 
by  tiny  projections  called  papillce.  These  papillae  contain  organs 
known  as  taste  buds,  the  sensory  endings  of  which  determine  the 
taste  of  substances.  The  tongue  is  used  in  moving  food  about  in 
the  mouth,  and  in 
starting  it  on  its  way 
to  the  gullet;  it  also 
plays  an  important 
part  in  speaking. 

The  Teeth.  —  In 
man  the  teeth,  unlike 
those  of  the  frog,  are 
used  in  the  mechanical 
preparation  of  the  food 
for  digestion.  Instead 
of  holding  prey,  they 
crush,  grind,  or  tear 
food  so  that  more  sur- 
face may  be  given  for 
the  action  of  the  diges- 
tive fluids.  The  teeth 
of  man  are  divided,  ac- 
cording to  their  func- 
tions, into  four  groups. 
In  the  center  of  both  the  upper  and  lower  jaw  in  front  are  found 
eight  teeth  with  chisel-like  edges,  four  in  each  jaw;  these  are 
the  incisors,  or  cutting  teeth.  Next  is  found  a  single  tooth  on 
each  side  (four  in  all) ;  these  have  rather  sharj)  i)uiuts  and  are 
called  the  canines.     Then  come  two  teeth  on  each  side,  eight  in 


I.    Teeth  of  the  upper  jaw,  from  below 


in- 


cisors; 3,  canine;  4,5,  premolars;  0,  7,  8,  molars. 
II.  longitudinal  section  of  a  tooth.  E,  enamel ; 
D,  dentine  ;  C,  cement ;  P,  pulp  cavity. 


302  DIGESTION  AND  ABSORPTION 

all,  called  premolars.  Lastly,  the  flat-top  molars,  or  grinding  teetn, 
of  which  there  are  six  in  each  jaw.  Food  is  caught  between 
irregular  projections  on  the  surface  of  the  molars  and  crushed 
to  a  pulpy  mass. 

Hygiene  of  the  Mouth.  —  Food  should  simply  be  chewed  and  rel- 
ished, with  no  thought  of  swallowing.  There  should  be  no  more  ef- 
fort to  prevent  than  to  force  swallowing.  It  will  be  found  that  if  you 
attend  only  to  the  agreeable  task  of  extracting  the  flavors  of  your 
food,  Nature  will  take  care  of  the  swallowing,  and  this  will  become, 
like  breathing,  involuntary.  The  instinct  by  which  most  people 
eat  is  perverted  through  the  "  hurr}^  habit  "  and  the  use  of  abnor- 
mal foods.  Thorough  mastication  takes  time,  and  therefore  one 
must  not  feel  hurried  at  meals  if  the  best  results  are  to  be  secured. 
The  stopping  point  for  eating  should  be  at  the  earliest  moment  after 
one  is  really  satisfied. 

Care  of  the  Teeth.  —  It  has  been  recently  found  that  fruit  acids 
are  very  beneficial  to  the  teeth.  Vinegar  diluted  to  about  half 
strength  with  water  makes  an  excellent  dental  wash.  Clean  your 
teeth  carefully  each  morning  and  before  going  to  bed.  Use  dental 
silk  after  meals.  We  must  remember  that  the  bacteria  which 
cause  decay  of  the  teeth  are  washed  down  into  the  stomach  and 
may  do  even  more  harm  there  than  in  the  mouth. 

How  Food  is  Swallowed.  —  After  food  has  been  chewed  and 
mixed  with  saliva,  it  is  rolled  into  little  balls  and  pushed  by  the 
tongue  into  such  position  that  the  muscles  of  the  throat  cavity 
may  seize  it  and  force  it  downward.  Food,  in  order  to  reach  the 
gullet  from  the  mouth  cavity,  must  pass  over  the  opening  into 
the  windpipe.  When  food  is  in  the  course  of  being  swallowed, 
the  upper  part  of  this  tube  forms  a  trapdoor  over  the  opening. 
When  this  trapdoor  is  not  closed,  and  food  "  goes  down  the  wrong 
way,"  we  choke,  and  the  food  is  expelled  by  coughing. 

The  Gullet,  or  Esophagus.  —  Like  the  rest  of  the  food  tube 
the  gullet  is  lined  by  soft  and  moist  mucous  membrane.  The 
wall  is  made  up  of  two  sets  of  muscles,  —  the  inside  ones  running 
around  the  tube ;  the  outer  layer  of  muscle  taking  a  longitudinal 
course.  After  food  leaves  the  mouth  cavity,  it  gets  beyond  our 
direct  control,  and  the  muscles  of  the  gullet,  stimulated  to  activity 


DIGESTION   AND   ABSORPTION  303 

b}^  the  presence  of  food  in  the  tube,  push  the  food  down  to  the 
stomach  by  a  series  of  contractions  until  it  reaches  the  stom.'ich. 
These  wavelike  movements  (called  peristaltic  movements)  are 
characteristic  of  other  parts  of  the  food  tube,  food  bein^  ])uslied 
along  in  the  stomach  and 
the  small  intestine  by  a 
series  of  slow-moving  mus- 
cular waves.  Peristaltic 
movement    is    caused    by  bolus  ojjood 

muscles      which       are      not  Peristaltic  waves  on  the  gullet  of  maa. 

(A  bolus  means  little  ball.) 

under    voluntary    nervous 

control,  although  anger,  fear,  or  other  unpleasant  emotions  have 

the  effect  of  slowing  them  up  or  even  stopping  them  entirely. 

Stomach  of  Man.  —  The  stomach  is  a  pear-shaped  organ 
capable  of  holding  about  three  pints.  The  end  opposite  to  the 
gullet,  which  empties  into  the  small  intestine,  is  provided  with  a 
ring  of  muscle  forming  a  valve  called  the  pylorus.  There  is  also 
another  ring  of  muscle  guarding  the  entrance  to  the  stomach. 

Gastric  Glands.  —  If  we  open  the  stomach  of  the  frog,  and 
remove  its  contents  by  carefully  washing,  its  wall  is  seen  to  be 
thrown  into  folds  internally.  Between  the  folds  in  the  stomach  of 
man,  as  well  as  in  the  frog,  are  located  a  number  of  tiny  pits. 
These  form  the  mouths  of  the  gastric  glands,  which  pour  into  the 
stomach  a  secretion  known  as  the  gastric  juice.  The  gastric  glands 
are  little  tubes,  the  lining  of  which  secretes  the  fluid.  When  we 
think  of  or  see  appetizing  food,  this  secretion  is  given  out  in  con- 
siderable quantity.  The  stomach,  like  the  mouth,  '^  waters  " 
at  the  sight  of  food.  Gastric  juice  is  slightly  acid  in  its  chemical 
reaction,  containing  about  .2  per  cent  free  hydrochloric  acid.  It  also 
contains  two  very  important  enzymes,  one  called  pepsin,  and  an- 
other less  important  one  called  rennin. 

Action  of  Gastric  Juice.  —  If  protein  is  treated  with  artificial 
gastric  juice  at  the  temperature  of  the  body,  it  will  l)e  found  to 
become  swollen  and  then  gradually  to  change  to  a  substance 
which  is  soluble  in  water.  This  is  like  the  action  of  the  gastric 
juice  upon  proteins  in  the  stomach. 

The  other  enzyme  of  gastric  juice,  called  rennin,  curdles  or  coag- 


304 


DIGESTION  AND  ABSORPTION 


ulates  a  protein  found  in  milk;  after  the  milk  is   curdled,   the 
pepsin  is  able  to  act  upon  it.     ''  Junket"  tablets,  which  contain 

rennin,  are  used  in  the  kitchen  to  cause  this 
change. 

The  hydrochloric  acid  fomid  in  the  gastric 
juice  acts  upon  lime  and  some  other  salts 
taken  into  the  stomach  with  food,  changing 
them  so  that  they  may  pass  into  the  blood 
and  eventually  form  the  mineral  part  of  bone 
or  other  tissue.  The  acid  also  has  a  decided 
antiseptic  influence  in  preventing  growth  of 
bacteria  which  cause  decay,  and  some  of  which 
might  cause  disease. 

Movement  of  Walls  of  Stomach.  — The  stomach 
walls,  provided  with  three  layers  of  muscle  which 
run  in  an  oblique,  circular,  and  longitudinal  direc- 
tion  (taken   from  the   inside   outward),  are  well 
fitted  for  the  constant  churning  of  the  food  in 
A  peptic  gland,  from  the  ^j-^^t  organ.     Here,  as  elsewhere  in  the  digestive 
magrTified.^  a!  central  t^act,  the  muscles  are  involuntary,  muscular  action 
or   chief   cell,   which  being  under  the  control  of  the  so-called  sympathetic 

makes  pepsm ;  B,  bor-   ^i^j-pQus  system.      Food  material   in  the  stomach 

der  cells,  which  make  ,  ,  i   j        •        •,      i      •        ii 

acid.     (From  Miller's  makes  several  complete  cn-cuits  durmg  the  process 

Histology.)  of  digestion  in  that  organ.     Contrary  to  common 

belief,   the   greatest  amount  of  food  is  digested 

after  it  leaves  the  stomach.     But  this  organ  keeps  the  food  in  it  in 

almost  constant  motion  for  a  considerable  time,  a  meal  of  meat  and 

vegetables  remaining  in  the  stomach  for  three  or  four  hours.     While 

movement  is  taking  place,  the  gastric  juice  acts  upon  proteins,  softening 

them,  while  the  constant  churning  movement  tends  to  separate  the  bits 

of  food  into  finer  particles.     Ultimately  the  semifluid  food,  much  of  it  still 

undigested,  is  allowed  to  pass  in  small  amounts  through  the  pyloric  valve, 

into  the  small  intestine.     This  is  allowed  by  the  relaxation  of  the  ringhke 

muscles  of  the  pylorus. 

Experiments  on  Digestion  in  the  Stomach.  —  Some  very  inter- 
esting experiments  have  recently  been  made  by  Professor  Cannon 
of  Harvard  with  reference  to  movements  of  the  stomach  contents. 
Cats  were  fed  with  material  having  in  it  bismuth,  a  harmless 


DIGESTION  AND  ABSORPTION 


30rj 


chemical  that  would  be  visible  under  the  X-ray.  It  was  found 
that  shortly  after  food  reached  the  stomach  a  series  of  waves  began 
which  sent  the  food  toward  the  pyloric  end  of  the  stomach.  If 
the  cat  was  feeling  happy  and  well,  these  contractions  continued 
regularly,  but  if  the  cat  was  cross  or  bad  tempered,  the  movements 
would  stop.  This  shows  the  importance  of  cheerfulness  at  meals. 
Other  experiments  showed  that  food  whicli  was  churned  into  a 
soft  mass  was  only  permitted  to  leave  the  stomach  when  it  })ecame 
thoroughly  permeated  by  the  gastric  juice.  It  is  the  acid  in 
the  partly  digested  food  that  causes  the  stomach  valve  to  open  and 
allow  its  contents  to  escape  little  by  little  into  the  small  intestine. 

The  partly  digested  food  in  the  small  intestine  almost  imme- 
diately comes  in  contact  with  fluids  from  two  glands,  the  liver  and 
pancreas.     We  shall  first  consider  the  function  of  the  pancreas. 

Position  and  Structure  of  the  Pancreas.  —  The  most  important 
digestive  gland  in  the  human  body  is  the  pancreas.  The  gland 
is  a  rather  diffuse  structure ;  its  duct  empties  by  a  common  opc^iing 
with  the  bile  duct  into  the  small  intestine,  a  short  distance  below 
the  pylorus.  In  internal  structure,  the  pancreas  resembles  the 
salivary  glands. 

Work  done  by  the  Pancreas.  —  Starch  paste  added  to  artificial 
pancreatic  fluid  and  kept  at  blood  heat  is  soon  changed  to  sugar. 
Protein,  under  the  same  conditions,  is  changed  to  a  peptone. 


%  J. 

ooc*" 


0     'i*^ 

'  '<.*.. 


A 


Appearance  of  milk  under  the  mitToscope,  showing  th<>  natural  grouping  of 
the  fat  globules.  In  the  circle  a  single  group  is  highly  magnified. 
Milk  is  one  form  of  an  emulsion.     (S.  M.  Babcock,  Wis.  Bui.  No.  Gl.) 

HUNTER,    CIV.   BI.  —  20 


306  DIGESTION   AND   ABSORPTION 

Fats,  which  so  far  have  been  unchanged  except  to  be  melted  by  the 
heat  of  the  body,  are  changed  by  the  action  of  the  pancreas  into 
a  form  whicli  can  pass  through  the  wails  of  the  food  tube.  If  we 
test  pancreatic  fluid,  we  find  it  strongly  alkaline  in  its  reaction. 
If  two  test  tubes,  one  containing  olive  oil  and  water,  the  other 
olive  oil  and  a  weak  solution  of  caustic  soda,  an  alkali,  be  shaken 
violently  and  then  allowed  to  stand,  the  oil  and  water  will  quickly 
separate,  while  the  oil,  caustic  soda,  and  water  will  remain  for 
some  time  in  a  milky  emulsion.  If  this  emulsion  be  examined 
under  the  microscope,  it  will  be  found  to  be  made  of  millions  of 
little  droplets  of  fat,  floating  in  the  liquid.  The  presence  of  the 
caustic  soda  helped  the  forming  of  the  emulsion.  Pancreatic 
fluid  similarly  emulsifies  fats  and  changes  them  into  soft  soaps  and 
fatty  acids.  Fat  in  this  form  may  be  absorbed.  The  process  of 
this  transformation  is  not  well  understood. 

Conditions  under  which  the  Pancreas  does  its  Work.  —  The 
secretion  from  this  gland  seems  to  be  influenced  by  the  overflow  of 
acid  material  from  the  stomach.  This  acid,  on  striking  the  lining 
of  the  small  intestine,  causes  the  formation  in  its  walls  of  a  sub- 
stance known  as  secretin.  This  secretin  reaches  the  blood  and 
seems  to  stimulate  all  the  glands  pouring  fluid  into  the  intestine 
to  do  more  work.  A  pint  or  more  of  pancreatic  fluid  is  secreted 
every  day. 

The  Intestinal  Fluid.  —  Three  different  pancreatic  enzymes  do 
the  work  of  digestion,  one  acting  on  starch,  another  on  protein,  and 
a  third  on  fats.  It  has  been  found  that  some  of  these  enzymes  will 
not  do  their  work  unless  aided  by  the  intestinal  fluid,  a  secretion 
formed  in  glands  in  the  walls  of  the  small  intestine.  This  fluid, 
though  not  much  is  known  about  it,  is  believed  to  play  an  important 
part  in  the  digestion  of  all  lands  of  foods  left  undigested  in  the 
small  intestine. 

Liver.  —  The  liver  is  the  largest  gland  in  the  body.  In  man,  it 
hangs  just  below  the  diaphragm,  a  little  to  the  right  side  of  the 
body.  During  life,  its  color  is  deep  red.  It  is  divided  into  three 
lobes,  between  two  of  which  is  found  the  gall  bladder,  a  thin-walled 
sac  which  holds  the  bile,  a  secretion  of  the  liver.  Bile  is  a  strongly 
alkahne  fluid  of  greenish  color.     It  reaches  the  intestine  through 


DIGESTION  AND  ABSORPTION 


307 


the  same  opening  as  the  pancreatic  fluid.  Almost  one  quart  of 
bile  is  passed  daily  into  the  digestive  canal.  The  color  of  bile  is 
due  to  certain  waste  substances  which  come  from  the  destruction 
of  worn-out  red  corpuscles  of  the  blood.  This  destruction  takes 
place  in  the  liver. 

Functions  of  Bile.  —  The  action  of  bile  is  not  very  well  known. 
It  has  the  very  important  faculty  of  aiding  the  pancreatic  fluid  in 
digestion,  though  alone  it 
has  sligh{  if  any  digestive 
power.  Certain  substances 
in  the  bile  aid  especially  in 
the  absorption  of  fats. 
Bile  seems  to  be  mostly  a 
waste  product  from  the 
blood  and  as  such  inci- 
dentally serves  to  keep  the 
contents  of  the  intestine  in 
a  more  or  less  soft  condi- 
tion, thus  preventing  ex- 
treme constipation. 

The  Liver  a  Storehouse. 
—  Perhaps  the  most  impor- 
tant function  of  the  Hver  is 
the  formation  within  it  of  a 
material  called  glycogen,  or  Diagram  of  a  bit  of  the  wall  of  the  small  in- 
animal    starch.      The    liver        ^^^^^^^   greatly    magnifiod.      a,   mouths    of 

intestinal   glands;    o,  villus   cut    lengthwise 
IS   supplied   by   blood   from         to  show  blood  vessels  and  lacteal  (in  center) ; 

two    sources.      The   greater         ':    ^.^f^^!   sending    branches    to  other  villi; 

®     ,  I,    intestinal    glands;     tn,    artery;    v,    vein; 

amount   of    blood    received         l,  t,  muscular  coats  of  intestine  wall. 

by  the  liver  comes  directly 

from  the  walls  of  the  stomach  and  intestine  to  this  organ.  It 
normafly  contains  about  one  fifth  of  all  the  blood  in  the  body. 
This  blood  is  very  rich  in  food  materials,  and  from  it  the  cells  of 
the  liver  take  out  sugars  to  form  glycogen.^  Glycogen  is  stored 
in  the  liver  until  such  a  time  as  a  food  is  needed  that  can  be  quickly 


1  It  is  known  that  glycogen  may  be  formed  in  the  body  from  protein,  and  possibly 
from  fatty  foods. 


308  DIGESTXON  AND  ABSORPTION 

oxidized ;  then  it  is  changed  to  sugar  and  carried  off  by  the  blood 
to  the  tissue  which  requires  it,  and  there  used  for  this  purpose. 
Glycogen  is  also  stored  in  the  muscles,  where  it  is  oxidized  to  release 
energy  when  the  muscles  are  exercised. 

The  Absorption  of  Digested  Food  into  the  Blood.  —  The  object 
of  digestion  is  to  change  foods  from  an  insoluble  to  a  soluble  form. 
This  has  been  seen  in  the  study  of  the  action  of  the  various  diges- 
tive fluids  in  the  body,  each  of  which  is  seen  to  aid  in  dissolving 
solid  foods,  changing  them  to  a  fluid,  and,  in  case  of  the  bile, 
actually  assisting  them  to  pass  through  the  wall  of  the  intestine. 
A  small  amount  of  digested  food  may  be  absorbed  by  the  blood 
in  the  blood  vessels  of  the  walls  of  the  stomach.  Most  of  the 
absorption,  however,  takes  place  through  the  walls  of  the  small 
intestine. 

Structure  of  the  Small  Intestine.  —  The  small  intestine  in  man  is  a 
slender  tube  nearly  twenty  feet  in  length  and  about  one  inch  in  diameter. 
If  the  chief  function  of  the  small  intestine  is  that  of  absorption,  we  must 
look  for  adaptations  which  increase  the  absorbing  surface  of  the  tube. 
This  is  gained  in  part  by  the  inner  surface  of  the  tube  being  thrown  into 
transverse  folds  which  not  only  retard  the  rapidity  with  which  food  passes 
down  the  intestine,  but  also  give  more  absorbing  surface.  But  far  more 
important  for  absorption  are  millions  of  Uttle  projections  which  cover  the 
inner  surface  of  the  small  intestine. 

The  Villi.  — So  numerous  are  these  projections  that  the  whole 
surface  presents  a  velvety  appearance.  Collectively,  these  struc- 
tures are  called  the  villi  (singular  villus).  They  form  the  chief 
organs  of  absorption  in  the  intestine,  several  thousand  being 
distributed  over  every  square  inch  of  surface.  By  means  of  the 
folds  and  villi  the  small  intestine  is  estimated  to  have  an  absorb- 
ing surface  equal  to  twice  that  of  the  surface  of  the  body.  Between 
the  villi  are  found  the  openings  of  the  intestinal  glands. 

Internal  Structure  of  a  Villus.  —  The  internal  structure  of  a 
villus  is  best  seen  in  a  longitudinal  section.  We  find  the  outer 
wall  made  up  of  a  thin  layer  of  cells,  the  epithelial  layer.  It  is 
the  duty  of  these  cells  to  absorb  the  semifluid  food  from  within  the 
intestine.     Underneath  these  cells  lies  a  network  of  very  tiny  blood 


DIGESTION  AND  ABSORPTION 


.309 


iH^m  to 
arm 


vessels,  while  inside  of  these,  occupying  the  core  of  the  vilhis,  are 
found   spaces   which,    because   of   their   white   appearance   after 
absorption  of  fats,  have  been  called  ladeals.    (See  figure*,  i)age  207.) 
Absorption  of  Foods.  —  Let  us  now  attempt  to  find  out  exactly 
how  foods  are  passed  from  the  intestines  into  the  blood.     Food 
substances  in  solution  may  be  soaked  up  as  a  sponge  would  take  up 
water,  or  they  may  pass  by  osmosis  into  the  cells  lining  tlie  villus. 
These  cells  break  down  the  peptones  into 
a  substance  that  will  pass  into  and  be- 
come part  of  the  blood.     Once  within  the 
villus,  the  sugars  and  digested  proteins 
pass  through  tiny  blood  vessels  into  the 
larger  vessels  comprising  the  portal  cir- 
culation.    These  pass  through  the  liver, 
where,  as  we  have  seen,  sugar  is  taken 
from  the  blood  and  stored  as  glycogen. 
From  the  liver,  the  food  within  the  blood 
is  sent  to  the  heart,  from  there  is  pumped 
to  the  lungs,  from  there  returns  to  the 
heart,  and  is  pumped  to  the  tissues  of  the 
body.      A   large   amount  of   water   and 
some  salts  are  also  absorbed  through  the 
walls  of  the  stomach  and  intestine  as  the 
food  passes  on  its  course.     The  fats  in 
the  form  of  soaps  and  fatty  acids  pass 
into  the  space  in  the  center  of  the  villus. 
Later  they  are  changed  into  fats  again, 
probably  in  certain  groups  of  gland  cells 
known  as  mesenteric  glands,  and  eventually  reach  the  blood  by 
way  of  the  thoracic  duct  without  passing  through  the  liver. 

Large  Intestine.  — The  large  intestine  has  somewhat  the  same  struc- 
ture as  the  small  intestine,  except  that  it  lacks  the  villi  and  has  a  greater 
diameter.  Considerable  absorption,  however,  takes  place  through  its 
walls  as  the  mass  of  food  and  refuse  material  is  slowly  pushed  along  by 
the  muscles  within  its  walls. 

Vermiform  Appendix.  —  At  the  point  where  the  small  intestine  widens 
to  form  the  large  intestine,  a  baglike  pouch  is  formed.     From  one  side  of 


Diagram    to    show    how    the 
nutrients  reach  the  blood. 


310  DIGESTION   AND   ABSORPTION 

this  pouch  is  given  off  a  small  tube  about  four  inches  long,  closed  at  the 
lower  end.  This  tube,  the  rudiment  of  what  is  an  important  part  of  the 
food  tube  in  the  lower  vertebrates,  is  called  the  vermiform  appendix-  It 
has  come  to  have  unpleasant  notoriety  in  late  years,  as  the  site  of  serious 
inflammation. 

Constipation.  —  In  the  large  intestine  live  millions  of  bacteria, 
some  of  whicli  make  and  give  olT  poisonous  substances  known 
as  toxins.  These  substances  are  easily  absorbed  through  the 
walls  of  the  large  intestine,  and,  when  they  pass  into  the  blood, 
cause  headaches  or  sometimes  serious  trouble.  Hence  it  follows 
that  the  lower  bowel  should  be  emptied  of  this  matter  as  fre- 
quently as  possible,  at  least  once  a  day.  Constipation  is  one  of 
the  most  serious  evils  the  American  people  have  to  deal  with,  and 
it  is  largely  brought  about  by  the  artificial  life  which  v^e  lead,  with 
its  lack  of  exercise,  fresh  air,  and  sleep.  Fruit  with  meals,  espe- 
cially at  breakfast,  plenty  of  water  between  meals  and  before 
breakfast,  exercise,  particularly  of  the  abdominal  muscles,  and 
regular  habits  will  all  help  to  correct  this  evil. 

Hygienic  Habits  of  Eating ;  the  Causes  and  Prevention  of  Dys- 
pepsia. —  From  the  contents  of  the  foregoing  chapter  it  is  evident 
that  the  object  of  the  process  of  digestion  is  to  break  up  solid  food 
so  that  it  may  be  absorbed  to  form  part  of  the  blood.  Any  habits 
we  may  form  of  thoroughly  chewing  our  food  will  evidently  aid 
in  this  process.  Undoubtedly  much  of  the  distress  known  ay 
dyspepsia  is  due  to  too  hasty  meals  with  consequent  lack  of  proper 
mastication  of  food.  The  message  of  Mr.  Horace  Fletcher  in 
bringing  before  us  the  need  of  proper  mastication  of  food  and  the 
attendant  evils  of  overeating  is  one  which  we  cannot  afford  to 
ignore.  It  is  a  good  rule  to  go  away  from  the  table  feeling  a  little 
hungry.  Eating  too  much  overtaxes  the  digestive  organs  and  pre  • 
vents  their  working  to  the  best  advantage.  Still  another  cause  of 
dyspepsia  is  eating  when  in  ^fatigued  condition.  It  is  always  a  good 
plan  to  rest  a  short  time  before  eating,  especially  after  any  hard  man- 
ual work.  We  have  seen  how  great  a  part  unpleasant  emotions  play 
in  preventing  peristaltic  movements  of  the  food  tube.  Conversely, 
pleasant  conversation,  laughter,  and  fun  will  help  you  to  digest  your 
meal.     Eating  between  meals  is  condemned  by  physicians  because 


DIGESTION   AND   ABSORPTION 


311 


it  calls  the  blood  to  the  digestive  organs  at  a  time  when  it  should  be 
more  active  in  other  parts  of  the  body. 

Effect  of  Alcohol  on  Digestion.  —  It  is  a  well-known  fact  that 
alcohol  extracts  water  from  tissues  with  which  it  is  in  contact. 
This  fact  works  much  harm  to  the  interior  surface  of  the  food  tube, 
especially  the  walls  of  the  stomach,  which  in  the  case  of  a  hard 
drinker  are  likely  to  become  irritated  and  much  toughened.  In 
very  small  amounts  alcohol  stimulates  the  secretion  of  the  sali- 
vary and  gastric  glands,  and  thus  appears  to  aid  in  digestion. 
'  The  following  results  of  experiments  on  dogs,  published  in  the 
American  Journal  of  Physiology,  Vol.  I,  Professor  Chittenden  of 
Yale  University  gives  as  ''  strictly  comparable,"  because  "  they 
were  carried  out  in  succession  on  the  same  day."  They  show 
that  alcohol  retards  rather  than  aids  in  digestion  :  — 


Number 

OF  Experiment 

is  Lb.  Meat  with  Water 

is  Lb.  Meat  with  Dilute 
Alcohol 

XVII 

a  9 :  15  A.M. 

Digested  in  3  hours 

XVII 

/3  3  :  00  P.M. 

Digested  in  3:15  hours 

XVIII 

a  8  :30  a.m. 

Digested  in  2 :  30  hours 

XVIII 

^  2  :  10  P.M. 

Digested  in  3 :  00  hours 

XIX 

«  9 :  00  A.M. 

Digested  in  2 :  30  hours 

XIX 

/3  2  :  30  P.M. 

Digested  in  3 :  00  hours 

XX 

a  9 :  15  A.M. 

Digested  in  2 :  -45  hours 

XX 

/3  2 :  30  P.M. 

Digested  in  2 :  15  hours 

VI 

a.  9;  15  A.M. 

Digested  in  3 :  45  hours 

VI 

/3  1 :  00  P.M. 

Digested  in  3 :  15  hours 

Average 

2 :  42  hours 

3 :  09  hours 

As  a  result  of  his  experiments,  Professor  Chittenden  remarks: 
*'  We  believe  that  the  results  obtained  justify  the  conclusion  that 
gastric  digestion  as  a  whole  is  not  materially  modified  by  the 
introduction  of  alcoholic  fluids  with  the  food.  In  other  words, 
the  unquestionable  acceleration  of  gastric  secretion  which  follows 
the  ingestion  of  alcoholic  beverages  is,  as  a  rule,  counterbalanced 
by  the  inhibitory  effect  of  the  alcoholic  fluids  upon  the  chemical 


312 


DIGESTION  AND  ABSORPTION 


process  of  gastric  digestion,  with  perhaps  at  times  a  tendency 
towards  preponderance  of  inhibitory  action."  Others  have  come 
to  the  same  or  stronger  conclusions  as  to  the  undesirable  action 
of  alcohol  on  digestion,  as  a  result  of  their  own  experiments. 

Effect  of  Alcohol  on  the  Liver.  —  The  effect  of  heavy  drinking 
upon  the  liver  is  graphically  shown  in  the  following  table  prepared 
by  the  Scientific  Temperance  Federation  of  Boston,  Mass. :  — 


Deaths  by: 

10        20        30         40       50         60        70        80        90 
1 1 i 1 1            1 1 '            ■            ' 

Accidents.        tea                         4587                         1 

Hul.  luoerculosis 

EH*!                        29.832 

Heart  Disease 

RW*!                        13225                       1 

A"po-plex^ 

2585 

9163                      1 

ParaVs               Wk^                                 1817                                  1 

"HneuTTLonia 

3090 

10.954                     1 

Arterial  Disease  ^^^SKM                              2158                                1 

Suiacle 

1388 

1                      4647                      1 

Brigkts  DisPasfi. 

^RMMM                \ZZ5S               1 

Cirrlaosisof  Liver. 

Z7GZ                UtMESMMl 

AlcoWolisra. 

zozs                        J 

TOTAL 

26507 

96,063                    1 

Proportion  of  deaths  from  disease  in  a  certain  area  due  to  alcohol.     The  black 

area  shows  deaths  due  to  alcohol. ^ 


"  AlcohoUc  indulgence  stands  almost  if  not  altogether  in  the 
front  rank  of  the  enemies  to  be  combated  in  the  battle  for  health." 
—  Professor  William  T.  Sedgwick. 

^  Does  not  include  deaths  from  general  alcoholic  paralysis  or  other  organic 
diseases  due  to  alcohol.  Liver  cirrhosis  due  to  alcohol  conservatively  estimated 
at  75  per  cent  of  total  cases. 


XXL     THE   BLOOD   AND   ITS   CIRCULATION 

rrohlems,  —  To  discover  the  coinpositioii  ami  uses  of  the  (Uf- 
f event  parts  of  the  blood. 

To  find  out  the  means  by  which  the  blood  is  circulated 
about  the  body. 

Laboratory  Suggestions 

Demonstration.  —  Structure  of  blood,  fresh  frog's  blood  and  human 
blood.     Drawings. 

Demonstration.  —  Clotting  of  blood. 

Demonstration.  —  Use  of  models  to  demonstrate  that  the  heart  is  a  force 
pump. 

Demonstration.  —  Capillary  circulation  in  web  of  frog's  foot  or  tadpole's 
tail.     Drawing. 

Home  or  laboratory  exercise.  —  On  relation  of  exercise  on  rate  of  heart 
beat. 

Function  of  the  Blood.  —  The  chief  function  of  the  digestive 
tract  is  to  change  foods  to  such  form  that  they  can  be  absor])ed 
through  the  walls  of  the  food  tube  and  become  part  of  the  blood. ^ 

If  we  examine  under  the  microscope  a  drop  of  blood  taken  from 
the  frog  or  man,  we  find  it  made  up  of  a  fluid  called  plasma  and  two 
kinds  of  bodies,  the  so-called  red  corpuscles  and  colorless  corpuscles, 
floating  in  this  plasma. 

Composition  of  Plasma.  —  The  plasma  of  blood  is  found  to  be 
largely  (about  90  per  cent)  water.  It  also  contains  a  considerable 
amount  of  protein,  some  sugar,  fat,  and  mineral  material.  It  is, 
then,  the  medium  which  holds  the  fluid  food  that  has  been  ab- 
sorbed from  within  the  intestine.  This  food  is  pum])(Ml  to  the  body 
cells  where,  as  work  is  performed,  oxidation  takes  i)lace  and  heat 
is  given  off  as  a  form  of  energy.     The  almost  constant  temperature^ 

1  This  change  is  due  to  the  action  of  certain  enzymes  upon  tht'  nutrii'iit.s  in  va- 
rious foods.  But  we  also  find  that  peptones  are  changed  back  again  to  proteins  wlu-n 
once  in  the  blood.  This  appears  to  be  due  to  the  reversible  action  of  the  enzymes 
acting  upon  them.     (See  page  307.) 

313 


314 


THE  BLOOD   AND   ITS   CIRCULATION 


Human  blood  as  seen  under  the 
high  power  of  the  compound 
microscope ;  at  the  extreme 
right  is  a  colorless  corpuscle. 


of  the  body  is  also  due  to  the  blood,  which  brings  to  the  surface  of 
the  body  much  of  the  heat  given  off  by  oxidation  of  food  in  the 

muscles  and  other  tissues.  When 
the  blood  returns  from  the  tissues 
where  the  food  is  oxidized,  the 
plasma  brings  back  with  it  to  the 
lungs  part  of  the  carbon  dioxide 
liberated  where  oxidation  has  taken 
place.  Some  waste  products,  to  be 
spoken  of  later,  are  also  found  in 
the  plasma. 

The  Red  Blood  Corpuscle ;  its 
Structure  and  Functions.  —  The 
red  corpuscle  in  the  blood  of  the 
frog  is  a  true  cell  of  disklike  form,  containing  a  nucleus.  The  red 
corpuscle  of  man  is  made  in  the  red  marrow  of  bones  and  in 
its  young  stages  has  a  nucleus.  In  its  adult  form,  however, 
it  lacks  a  nucleus.  Its  form  is  that  of  a  biconcave  disk.  So 
small  and  so  numerous  are  these  corpuscles  that  about  five 
million  are  found  in  a  cubic  millimete:*  of  normal  blood.  They 
make  up  almost  one  half  the  total  volume  of  the  blood.  The 
color,  which  is  found  to  be  a  dirty  yellow  when  separate  cor- 
puscles are  viewed  under  the  microscope,  is  due  to  a  protein 
material  called  hoemoglohin.  Haemoglobin  contains  a  large  amount 
of  iron.  It  has  the  power  of  uniting  Yerj  readily  with  oxygen 
whenever  that  gas  is  abundant,  and,  after  having  absorbed  it, 
of  giving  it  up  to  the  surrounding  media,  when  oxygen  is  there 
present  in  smaller  amounts  than  in  the  corpuscle.  This  function 
of  carrying  oxygen  is  the  most  important  function  of  the  red 
corpuscle,  although  the  red  corpuscle  also  removes  part  of  the 
carbon  dioxide  from  the  tissues  on  their  return  to  the  lungs.  The 
taking  up  of  oxygen  is  accompanied  by  a  change  in  color  of  the 
mass  of  corpuscles  from  a  dull  red  to  a  bright  scarlet. 

Clotting  of  Blood.  —  If  fresh  beef  blood  is  allowed  to  stand  overnight, 
it  will  be  found  to  have  separated  into  two  parts,  a  dark  red,  almost  solid 
clot  and  a  thin,  straw-colored  liquid  called  serum.  Serum  is  found  to 
be  made  up  of  about  90  per  cent  water,  8  per  cent  protein,  1  per  cent 


THE   BLOOD   AND   ITS   CIRCULATION 


315 


other  organic  foods,  and  1  per  cent  mineral  substances.  In  these 
respects  it  very  closely  resembles  the  fluid  food  that  is  absorbed  from 
the  intestines. 

If  another  jar  of  fresh  beef  blood  is  poured  into  a  i)an  and  briskly 
whipped  with  a  bundle  of  httle  rods  (or  with  an  egg  beater),  a  stringy  sub- 
stance will  be  found  to  stick  to  the  rods.  This,  if  washed  carefully,  is 
seen  to  be  almost  colorless.  Tested  with  nitric  acid  and  ammonia,  it  is 
found  to  contain  a  protein  substance  which  is  called  fibrin. 

Blood  plasma,  then,  is  made  up  of  a  fluid  portion  of  serum,  and 
fibrin,  which,  although  in  a  fluid  state  in  the  blood  vessels  witliin 
the  body,  coagulates  when  blood  is  removed  from  the  blood  vessels. 
This  coagulation  aids  in  making  a  blood  clot.  A  clot  is  simply  a 
mass  of  fibrin  threads  with  a  large  number  of  corpuscles  tangled 
within.  The  clotting  of  blood  is  of  great  physiological  importance, 
for  otherwise  we  might  bleed  to  death  even  from  a  small  wound. 

Blood  Plates.  —  In  blood  within  the  circulatory  system  of  the 
body,  the  fibrin  is  held  in  a  fluid  state  called  fibrinogen.  An 
enzyme,  acting  upon  this  fibrinogen,  the  soluble  protein  in  the 
blood,  causes  it  to  change  to  an  insoluble  form,  the  fibrin  of  the 
clot.  This  change  seems  to  be  due  to  the  action  of  minute  bodies 
in  the  blood  known  as  blood 
plates.  Under  abnormal 
conditions  these  blood 
plates  break  down,  releas- 
ing some  substances  which  A^Sl 
eventually  cause  this  en-  <3^ 
zyme  to  do  its  work.  '' 

The  Colorless  Corpuscle; 
Structure  and  Functions. — 
A  colorless  corpuscle  is  a 
cell  irregular  in  outline,  the 
shape  of  which  is  constantly 
changing.  These  corpuscles 
are  somewhat  larger  than  the  red  corpuscles,  but  less  numerous, 
there  being  about  one  colorless  corpuscle  to  every  three  hundred 
red  ones.  They  have  the  power  of  movement,  for  they  are  found 
not  only  inside  but  outside  the  blood  vessels,  showing  that  they 


.x'Tr)o 


A  small  artery  (A)  breaking  up  into  capillaries 
(c)  which  unit3  to  form  a  vein  (F).  Note 
at  (P)  several  colorless  corpuscles,  which  are 
fighting  bacteria  at  that  point. 


316 


THE  BLOOD   AND  ITS   CIRCULATION 


have  worked  their  way  between  the  cells  that  form  the  walls  of 
the  blood  tubes. 

A  Russian  zoologist,  Metchnikoff,  after  studying  a  number  of 
simple  animals,  such  as  medusae  and  sponges,  found  that  in  such 
animals  some  of  the  cells  lining  the  inside  of  the  food  cavity  take 
up  or  engulf  minute  bits  of  food.  Later,  this  food  is  changed  into 
the  protoplasm  of  the  cell.  Metchnikoff  ])elieved  that  the  colorless 
corpuscles  ot  the  blood  have  somewhat  the  same  function.     This 

he  later  proved  to  be  true.  Like  the 
amoeba,  they  feed  by  engulfing  their 
prey.  This  fact  has  a  very  important 
bearing  on  the  relation  of  colorless  cor- 
puscles to  certain  diseases  caused  by 
bacteria  within  the  body.  If,  for  ex- 
ample, a  cut  becomes  infected  by  bac- 
teria, inflammation  may  set  in.  Color- 
less corpuscles  at  once  surround  the 
spot  and  attack  the  bacteria  which 
cause  the  inflammation.  If  the  bac- 
teria are  few  in  number,  they  are  quickly 
eaten  by  certain  of  the  colorless  cor- 
puscles, which  are  known  as  phagocytes. 
If  bacteria  are  present  in  great  quan- 
tities,  they  may  prevail   and   kill   the 

A  colorless  corpuscle  catching       i  ,1  •         •  xi,  rni, 

and  eating  germs.  phagocytes   by   poisonmg   them.      The 

dead  bodies  of  the  phagocytes  thus 
killed  are  found  in  the  pus,  or  matter,  which  accumulates  in 
infected  wounds.  In  such  an  event,  we  must  come  to  the  aid  of 
nature  by  washing  the  wound  with  some  antiseptic,  as  weak 
carbolic  acid  or  hydrogen  peroxide. 

Antibodies  and  their  Uses.  —  In  case  of  disease  where,  for 
example,  fever  is  caused  by  poison  given  off  from  bacteria  we  find 
the  cells  of  the  body  manufacture  and  pour  into  the  blood  a 
substance  known  as  an  antibody.  This  substance  does  not  of 
necessity  kill  the  harmful  germs  or  even  stop  their  growth.  It 
does,  however,  unite  with  the  toxin  or  poison  given  off  by  the 
germs  and  renders  it  entirely  harmless. 


THE  BLOOD  AND  ITS  CIRCULATION 


317 


©  o 
o 


oa 


J 


Course  y  Pla^ijifi 


^^W}0i^y>J^^P^' 


Dissolved  I 
NiitrJejit 


■=-  lyymah  Space     ^^ 


^zJ^'-- Leucocyte 


LYMPH 


T^uiij- 


1 


Function  of  Lymph.  —  The  tissues  and  organs  of  the  body 
are  traversed  by  a  network  of  tubes  which  carry  the  blood.  Inside 
these  tubes  is  the  blood  proper,  consisting  of  a  fluid  plasma,  the 
colorless  corpuscles,  and  the  red  corpuscles.  Outside  the  blood 
tubes,  in  spaces  between  the  cells  which  form  tissues,  is  found 
another  fluid,  which  is  in  chemical  composition  very  much  like 
plasma  of  the  blood.  This  is  the  lymph.  It  is,  in  fact,  fluid  food 
in  which  some  colorless  amoeboid  corpuscles  are  found  Blood 
gives  up  its  food  material  to  the  lymph.  This  it  does  by  passing  it 
through  the  walls  of  the 
capillaries.  The  food  is  in  "^^ 
turn  given  up  to  the  tissue  SLoS)^ 
cells,  which  are  bathed  by  YmE^ 
the  lymph. 

Some  of  the  amoeboid 
corpuscles  from  the  blood 
make  their  way  between 
the  cells  forming  the  walls 
of  the  capillaries.  Lymph, 
then,  is  practically  hlood 
plasma  plus  some  colorless 
corpuscles.  It  acts  as  the 
medium  of  exchange  between 
the  hlood  proper  and  the  cells 
in  the  tissues  of  the  body. 
By  means  of  the  food  sup- 


ply  thus    brought,  the    cells  ^^^^  exchange  between  blood  and  the  cells  of 

of  the  body  are  able  to  grow,  the  body. 

the  fluid  food  being  changed 

to  the  protoplasm  of  the  cells.     By  means  of  the  oxygon  passed 

over  by  the  lymph,  oxidation  may  take  place  within  the  cells. 

Lymph  not  only  gives  food  to  the  cells  of  the  body,  ])ut  also  takes 

away  carbon  dioxide  and  otherwaste  materials,  which  are  ultimately 

passed  out  of  the  body  by  means  of  the  lungs,  skin,  and  kidneys. 

Internal  Secretions.  —  In  addition  to  all  the  functions  given 
above,  the  blood  has  recently  been  shown  to  carry  the  secretions  of 
a  number  of  glands  through  which  it  passes,  although  tliese  glands 


\ 


318  THE   BLOOD  AND   ITS   CIRCULATION 

have  no  ducts  to  carry  off  their  secretions.  These  internal  secre- 
tions seem  absolutely  necessary  for  the  health  of  the  body. 
Several  glands,  the  thyroid,  adrenal  bodies,  the  testes,  and  ovaries, 
as  well  as  the  pancreas,  give  off  these  remarkable  substances. 

The  Amount  of  Blood  and  its  Distribution.  —  Blood  forms,  by  weight, 
about  one  sixteenth  of  the  body.  This  would  be  about  four  quarts  to  a 
body  weight  of  130  pounds.  Normally,  about  one  half  of  the  blood  of 
the  body  is  found  in  or  near  the  organs  lying  in  the  body  cavity  below 
the  diaphragm,  about  one  fourth  in  the  muscles,  and  the  rest  in  the 
head,  heart,  lungs,  large  arteries,  and  veins. 

Blood  Temperature.  —  The  temperature  of  blood  in  the  human  body 
is  normally  about  98.6°  Fahrenheit  when  tested  under  the  tongue  by  a 
thermometer,  although  the  temperature  drops  almost  two  degrees  after 
we  have  gone  to  sleep  at  night.  It  is  highest  about  5  p.m.  and  lowest 
about  4  A.M.  In  fevers,  the  temperature  of  the  body  sometimes  rises  to 
107° ;  but  unless  this  temperature  is  soon  reduced,  death  follows.  Any 
considerable  drop  in  temperature  below  the  normal  also  means  death. 
Body  heat  results  from  the  oxidation  of  food,  and  the  circulation  of  blood 
keeps  the  temperature  nearly  uniform  in  all  parts  of  the  body. 

Cold-blooded  Animals.  —  In  animals  which  are  called  cold-blooded, 
the  blood  has  no  fixed  temperature,  but  varies  with  the  temperature  of 
the  medium  in  which  the  animal  lives.  Frogs,  in  the  summer,  may  sit 
for  hours  in  water  with  a  temperature  of  almost  100°.  In  winter,  they 
often  endure  freezing  so  that  the  blood  and  lymph  within  the  spaces 
under  the  loose  skin  are  frozen  into  ice  crystals.  This  change  in  body 
temperature  is  evidently  an  adaptation  to  the  mode  of  life. 

Circulation  of  the  Blood  in  Man.  —  The  blood  is  the  carrying 
agent  of  the  body.  Like  a  railroad  or  express  company,  it  takes 
materials  from  one  part  of  the  human  organism  to  another.  This 
it  does  by  means  of  the  organs  of  circulation,  —  the  heart  and 
blood  vessels.  These  blood  vessels  are  called  arteries  where  they 
carry  blood  away  from  the  heart,  veins  where  they  bring  blood  back 
to  the  heart,  and  capillaries  where  they  connect  the  larger  blood 
vessels.  The  organs  of  circulation  thus  form  a  system  of  con- 
nected tubes  through  which  the  blood  flows. 

The  Heart ;  Position,  Size,  Protection.  —  The  heart  is  a  cone- 
shaped  muscular  organ  about  the  size  of  a  man's  fist.  It  is 
located  immediately  above  the  diaphragm,  and  lies  so  that  the 


THE   BLOOD  AND  ITS   CIRCULATION 


319 


muscular  apex,  which  points  downward,  moves  while  beating 
against  the  fifth  and  sixth  ribs,  just  a  little  to  the  left  of  the 
midline  of  the  body.  This  fact  gives  rise  to  the  notion  that  thc^ 
heart  is  on  the  left  side  of  the  ])ody.  The  hcnirt  is  surrounded 
by  a  loose  membranous  bag  called  tlu^  pericardium,  the  inner 
lining  of  which  secretes  a  fluid  in 
which  the  heart  lies.  When,  for  any 
reason,  the  pericardial  fluid  is  not 
secreted,  inflammation  arises  in  that 
region. 

Internal  Structure  of  Heart.  —  If 
we  should  cut  open  the  heart  of  a 
mammal  down  the  midlipe,  we  could 
divide  it  into  a  right  and  a  left  side, 
each  of  which  would  have  no  internal 
connection  with  the  other.  Each  side 
is  made  up  of  an  upper  thin-walled 
portion  with  a  rather  large  internal 
cavity,  the  auricle,  which  opens  into  Diagram  showing  the  front  half  of 
a  lower  smaller  portion  with  heavy 
muscular  walls,  the  ventricle.  Com- 
munication between  auricles  and 
ventricles  is  guarded  by  little  flaps 
or  valves.  The  auricles  receive  blood 
from  the  veins.  The  ventricles  pump 
the  blood  into  the  arteries. 

The  Heart  in  Action.  —  The  heart  is  constructed  on  the  same 
plan  as  a  force  pump,  the  valves  preventing  the  reflux  of  l^lood  into 
the  auricle  when  it  is  forced  out  of  the  ventricle.  Blood  enters 
the  auricles  from  the  veins  because  the  muscles  of  that  part  of 
the  heart  relax;  this  allows  the  space  within  the  auricles  to  fill. 
Almost  immediately  the  muscles  of  the  ventricles  relax,  thus  allow- 
ing blood  to  pass  into  the  chambers  within  the  ventricles.  Tlicn. 
after  a  short  pause,  during  which  time  the  muscles  of  the  heart  are 
resting,  a  wave  of  muscular  contraction  begins  in  the  auricles  and 
ends  in  the  ventricles,  with  a  sudden  strong  contraction  which 
forces  the  blood  out  into  the  arteries.     Blood  is  kept  on  its  course 


the  heart  cut  away :  a,  aorta  ; 
I,  arteries  to  the  lungs;  la,  left 
auricle  ;  Iv,  left  ventricle  ;  tti,  tri- 
cuspid valve  open ;  n,  bicuspid 
or  mitral  valve  closed  ;  p  and  r, 
veins  from  the  lungs;  ra,  right 
auricle ;  rv,  right  ventricle ; 
V,  vena  cava.  Arrows  show  di- 
rection of  circulation. 


320 


THE  BLOOD  AND  ITS  CIRCULATION 


by  the  valves,  which  act  in  the  same  manner  as  do  the  valves  in  a 
pump.     The  blood  is  thus  made  to  pass  into  the  arteries  upon 

the  contraction  of  the 
ventricle  walls. 

The  Course  of  the 
Blood  in  the  Body.  — 
Although  the  two  sides 
of  the  heart  are  separate 
and  distinct  from  each 
other,  yet  every  drop 
of  blood  that  passes 
through  the  right  heart 
likewise  passes  later 
through  the  left  heart. 
There  are  two  distinct 
systems  of  circulation 
in*  the  body.  The  pul- 
monary circulation  takes 
the  blood  through  the 
right  auricle  and  ven- 
tricle, to  the  lungs,  and  passes  it  back  to  the  left  auricle.  This 
is  a  relatively  short  circulation,  the  blood  receiving  in  the  lungs 
its  supply  of  oxygen,  and  there  giving  up  some  of  its  carbon 
dioxide.  The  greater  circulation  is  known  as  the  systemic  circu- 
lation; in  this  system,  the  blood  leaves  the  left  ventricle  through 
the  great  dorsal  aorta.  A  large  part  of  the  blood  passes  directly 
to  the  muscles ;  some  of  it  goes  to  the  nervous  system,  kidneys, 
skin,  and  other  organs  of  the  body.  It  gives  up  its  supply  of 
food  and  oxygen  in  these  tissues,  receives  the  waste  products  of 
oxidation  while  passing  through  the  capillaries,  and  returns  to 


The  heart  is  a  force  pump ;   prove  it  from  these 

diagrams. 


I.  Circulation  in  a  fish.     G,  gills ;    C,  capillaries  oi  the  body.     Notice  the  two- 

chambered  heart. 

II.  The  circulation  in  a  frog.  L,  the  lungs  ;  C,  the  capillaries.  Notice  the  hearf, 
has  three  chambers.  What  is  the  condition  of  blood  leaving  the  ventricle  to 
go  to  the  cells  of  the  body  ? 

III.  The  circulation  in  man.  //,  head  ;  ^.arrns;  L,  lungs;  *S,  stomach  ;  Lz,  liver; 
K,  kidney:  S.I.,  small  intestine;  L.I.,  large  intestine;  Le,  legs;  1,  right 
auricle ;  2,  right  ventricle ;  3,  left  ventricle ;  4,  left  auricle ;  d,  dorsal  aorta ;  6, 
vein  to  lungs. 


THE  BLOOD   AND   ITS   CIRCULATION  321 


'^wW 


HUNTER,    CIV.    BI. 21 


322 


THE   BLOOD  AND  ITS   CIRCULATION 


the  right  auricle  through  two  large  vessels  known  as  the  vence 
cavcB.  It  requires  only  from  twenty  to  thirty  seconds  for  the 
blood  to  make  the  complete  circulation  from  the  ventricle  back 
again  to  the  starting  point.  This  means  that  the  entire  volume  of 
blood  in  the  human  body  passes  three  or  four  thousand  times  a 
day  through  the  various  organs  of  the  body.^ 

Portal  Circulation.  —  Some  of  the  blood,  on  its  way  back  to  the  heart, 
passes  to  the  walls  of  the  food  tube  and  to  its  glands.  From  there  it  is  sent 
with  its  load  of  absorbed  food  to  the  liver.  Here  the  vein  which  carries 
the  blood  (called  the  portal  vein)  breaks  up  into  capillaries  around  the 
cells  of  the  Uver,  when  it  gives  up  sugar  to  be  stored  as  glycogen.  From 
the  liver,  blood  passes  directly  to  the  right  auricle.  The  portal  circula- 
tion, as  it  is  called,  is  the  only  part  of  the  circulation  where  the  blood 
passes  through  two  sets  of  capillaries  on  its  way  from  auricle  to  auricle. 

Circulation  in  the  Web  of  a  Frog's  Foot.  —  If  the  web  of  the  foot 
of  a  live  frog  or  the  tail  of  a  tadpole  is  examined  under  the  com- 


■d 


Capillary  circulation  in  the  web  of  a  frog's  foot,  as  seen  under  the  compound  micro- 
scope, a,  b,  small  veins ;  c,  pigment  cells  in  the  skin ;  d,  capillaries  in  which 
the  oval  corpuscles  are  seen  to  follow  one  another  in  single  series. 

1  See  Hough  and  Sedgwick,  The  Human  Mechanism,  page  136. 


i 


THE  BLOOD  AND   ITS  CIRCULATION  323 

pound  microscope,  a  network  of  blood  vessels  will  be  seen.  In 
some  of  the  larger  vessels  the  corpuscles  are  moving  rapidly  and 
in  spurts  ;  these  are  arteries.  The  arteries  lead  into  smaller  vessels 
hardly  greater  in  diameter  than  the  width  of  a  single  corpuscle. 
This  network  of  capillaries  may  be  followed  into  larger  veins  in 
which  the  blood  moves  regularly.  This  illustrates  the  condition 
in  any  tissue  of  man  where  the  arteries  break  up  into  capillaries, 
and  these  in  turn  unite  to  form  veins. 

Structure  of  the  Arteries.  —  A  distinct  difference  in  structure 
exists  between  the  arteries  and  the  veins  in  the  human  body.  The 
arteries,  because  of  the  greater  strain  received  from  the  blood  which 
is  pumped  from  the  heart,  have  thicker  muscular  walls,  and  in 
addition  are  very  elastic. 

Cause  of  the  Pulse.  —  The  'puhe,  which  can  easily  be  detected  by  press- 
ing the  large  artery  in  the  wrist  or  the  small  one  in  front  of  and  above  the 
external  ear,  is  caused  by  the  gushing  of  blood  through  the  arteries  after 
each  pulsation  of  the  heart.  As  the  large  arteries  pass  away  from  the 
heart,  the  diameter  of  each  individual  artery  becomes  smaller.  At  the 
very  end  of  their  course,  these  arteries  are  so  small  as  to  be  almost  mi- 
croscopic in  size  and  are  very  numerous.  There  are  so  many  that  if 
they  were  placed  together,  side  by  side,  their  united  diameter  would  be 
much  greater  than  the  diameter  of  the  large  artery  (aorta)  which  passes 
blood  from  the  left  side  of  the  heart.  This  fact  is  of  very  great  im]ior- 
tance,  for  the  force  of  the  blood  as  it  gushes  through  the  arteries  becomes 
very  much  less  when  it  reaches  the  smaller  vessels.  This  gushing  move- 
ment is  quite  lost  when  the  capillaries  are  reached,  first,  because  there  is 
so  much  more  space  for  the  blood  to  fill,  and  second,  because  there  is 
considerable  friction  caused  by  the  very  tiny  diameter  of  the  capillaries. 

Capillaries.  —  The  capillaries  form  a  network  of  minute  tubes 
everywhere  in  the  body,  but  especially  near  the  surface  and  in  the 
lungs.  It  is  through  their  walls  that  the  food  and  oxygen  piiss 
to  the  tissues,  and  carbon  dioxide  is  given  up  to  the  plasma.  Tliey 
form  the  connection  that  completes  the  system  of  circulation  of 
blood  in  the  body. 

Function  and  Structure  of  the  Veins.  —  If  the  arteries  are  supply 
pipes  which  convey  fluid  food  to  the  tissues,  then  the  veins  may 
be  likened  to  drain  pipes  which  carry  away  waste  material  from  the 


324 


THE  BLOOD  AND   ITS   CIRCULATION 


tissues.     Extremely  numerous  in  the  extremities  and  in  the  muscles 
and  among  other  tissues  of  the  body,  they,  like  the  branches  of  a 

tree,  become  larger  and  unite  with  each  other  as  they 

approach  the  heart. 

If  the  wall  of  a  vein  is  carefully  examined,  it  will  be 
found  to  be  neither  so  thick  nor  so  tough  as  an  artery  wall. 
When  empty,  a  vein  collapses ;  the  wall  of  an  artery  holds 
its  shape.  If  you  hold  j^our  hand  downward  for  a  little 
time  and  then  examine  it,  you  will  find  that  the  veins, 
which  are  relatively  much  nearer  the  surface  than  are  the 
arteries,  appear  to  be  very  much  knotted.  This  appear- 
ance is  due  to  the  presence  of  tiny  valves  within.  These 
valves  open  in  the  direction  of  the  blood  current,  but 
would  close  if  the  direction  of  the  blood  flow  should  be 
reversed  (as  in  case  a  deep  cut  severed  a  vein).  As  the 
pressure  of  blood  in  the  veins  is  much  less  than  in  the 
arteries,  the  valves  thus  aid  in  keeping  the  flow  of  blood 
in  the  veins  toward  the  heart.  The  higher  pressure  in 
arteries  and  the  suction  in  the  veins  (caused  by  the  enlarge- 
ment of  the  chest  cavity  in  breathine)  are  the  chief  factors 

V   1  ■ 

veirf    "no-    which  cause  a  steady  flow  of  blood  through  the  veins  in 
tice  the  thin    the  body. 

vein.  Lymph   Vessels.  —  The   lymph   is   collected   from 

the  various  tissues  of  the  body  by  means  of  a  number 
of  very  thin-walled  tubes,  which  are  at  first  very  tiny,  but  after 
repeated  connection  with  other  tubes  ultimately  unite  to  form 
large  ducts.  These  lymph  ducts  are  provided,  like  the  veins, 
with  valves.  The  pressure  of  the  blood  within  the  blood  vessels 
forces  continually  more  plasma  into  the  lymph ;  thus  a  slow 
current  is  maintained.  On  its  course  the  lymph  passes  through 
many  collections  of  gland  cells,  the  lymph  glands.  In  these  glands 
some  impurities  appear  to  be  removed  and  colorless  corpuscles  made. 
The  lymph  ultimately  passes  into  a  large  tube,  the  thoracic  duct, 
which  flows  upward  near  the  ventral  side  of  the  spinal  column,  and 
empties  into  the  large  subclavian  vein  in  the  left  side  of  the  neck. 
Another  smaller  lymph  duct  enters  the  right  subclavian  vein. 

The  Lacteals.  —  We  have  already  found  that  part  of  the  digested 
food  (chiefly  carbohydrates,  proteins,  salts,  and  water)  is  absorbed 


THE   BLOOD   AND   ITS   CIRCULATION 


32.^ 


directly  into  the  blood  throup;h  the  walls  of  the  villi  and  carried  to 

the  liver.     Fat,  however,  is  passed  into  the  spaces  in  th<'  central 

part  of  the  villi,  and  from  there  into  otlier  spactes  Ixitween  the 

tissues,   known  as   the   ladcals. 

The  lacteals  carry  the  fats  into 

the  blood  by  way  of  the  thoracic 

duct.     The  lacteals  and  lymph 

vessels  have  in  part  the  same 

course.      It  will   be   thus   seen 

that  lymph  at  different  parts  of 

its   course  would   have   a  very 

different  composition. 

The  Nervous  Control  of  the 
Heart  and  Blood  Vessels.  —  Al- 
though the  muscles  of  the  heart 
contract  and  relax  without  our  be- 
ing able  to  stop  them  or  force  them 
to  go  faster,  yet  in  cases  of  sudden 
fright,  or  after  a  sudden  blow,  the 
heart  may  stop  beating  for  a  short 
interval.  This  .shows  that  the  heart 
is  under  the  control  of  the  nervous 
system.     Two  sets  of  nerve  fibers, 

both  of  which  are  connected  with  the  central  nervous  system,  pass  to 
the  heart.  One  set  of  fibers  accelerates,  the  other  slows  or  inhibits,  the 
heart  beat.  The  arteries  and  veins  are  also  under  the  control  of  the 
sympathetic  nervous  system.  This  allows  of  a  change  in  the  diameter 
of  the  blood  vessels.  Thus,  blushing  is  due  to  a  sudden  rush  of  blood  to 
the  surface  of  the  body  caused  by  an  expansion  of  the  blood  vessels  at 
the  surface.  The  blood  vessels  of  the  body  are  always  full  of  blood.  This 
results  from  an  automatic  regulation  of  the  diameter  of  the  blood  tubes  by 
a  part  of  the  nervous  system  called  the  vasomotor  nerves.  These  nerves 
act  upon  the  muscles  in  the  walls  of  the  blood  vessels.  In  this  way,  each 
vessel  adapts  itself  to  the  amount  of  blood  in  it  at  a  given  time.  After 
a  hearty  meal,  a  large  supply  of  blood  is  needed  in  the  walls  of  the  stomach 
and  intestines.  At  this  time,  the  arteries  going  to  this  region  are  dilated 
so  as  to  receive  an  extra  supply.  When  the  brain  performs  hard  work, 
blood  is  supplied  in  the  same  manner  to  that  region.  Hence,  one  shouUl 
not  study  or  do  mental  work  immediately  after  a  hearty  meal,  for  blood 


The  lymph  vessels ;  the  dark  spots  are 
lymph  glands :  lac,  lacteals ;  re,  tho- 
racic duct. 


320 


THE   BLOOD  AND   ITS   CIRCULATION 


will  be  drawn  away  to  the  brain,  leaving  the  digestive  tract  with  an  in- 
sufficient supply.     Indigestion  may  follow  as  a  result. 

The  Effect  of  Exercise  on  the  Circulation.  —  It  is  a  fact  familiar 
to  all  that  the  heart  beats  more  violently  and  quickly  when  we  are 
doing  hard  work  than  when  we  are  resting.  Count  your  own  pulse 
when  sitting  quietly,  and  then  again  after  some  brisk  exercise  in  the 
gymnasium.  Exercise  in  moderation  is  of  undoubted  value,  be- 
cause it  sends  the  increased  amount  of  blood  to  such  parts  of  the 
body  where  increased  oxidation  has  been  taking  place  as  the  result 
of  the  exercise.  The  best  forms  of  exercise  are  those  which  give 
as  many  muscles  as  possible  work  —  walking,  out-of-door  sports, 
any  exercise  that  is  not  violent.  Exercise  should  not  be  attempted 
immediately  after  eating,  as  this  causes  a  withdrawal  of  blood  from 
the  digestive  tract  to  the  muscles  of  the  body.  Neither  should 
exercise  be  continued  after  becoming  tired,  as  poisons  are  then 
formed  in  the  muscles,  which  cause  the  feeling  we  call  fatigue. 
Remember  that  extra  work  given  to  the  heart  by  extreme  exercise 
may  injure  it,  causing  possible  trouble  with  the  valves. 

Treatment  of  Cuts  and 
Bruises.  —  Blood  which  oozes 
slowly  from  a  cut  will  usually 
stop  flowing  by  the  natural 
means  of  the  formation  of  a 
clot.  A  cut  or  bruise  should, 
however,  be  washed  in  a  weak 
solution  of  carbolic  acid  or 
some  other  antiseptic  in  order 
to  prevent  bacteria  from  ob- 
taining a  foothold  on  the  ex- 
posed flesh.  If  blood,  issuing 
from  a  wound,  gushes  in  dis- 
tinct pulsations,  then  we  know 
that  an  artery  has  been  sev- 
ered. To  prevent  the  flow  of 
blood,  a  tight  bandage  known 

Stopping  flow  of  blood  from  an  artery  by  tmirmnupt   mimt    hp   tied 

applying  a  tight  bandage  (ligature)  be-      ^^    ^    lOUrmquei   muSI    DC   Ilea 

tween  the  cut  and  the  heart.  between  the  cut  and  the  heart. 


THE   BLOOD   AND   ITS  CIRCULATION  327 

A  handkerchief  with  a  knot  placed  over  the  artery  may  stop 
bleeding  if  the  cut  is  on  one  of  the  limbs.  If  this  does  not  serve, 
then  insert  a  stick  in  the  handkerchief  and  twist  it  so  as  to  make 
the  pressure  around  the  limb  still  greater.  Thus  we  may  close 
the  artery  until  the  doctor  is  called,  who  may  sew  up  the  injured 
blood  vessel. 

The  Effect  of  Alcohol  upon  the  Blood.  —  It  has  recently  been 
discovered  that  alcohol  has  an  extremely  injurious  effect  upon  the 
colorless  corpuscles  of  the  blood,  lowering  their  ability  to  fight 
disease  germs  to  a  marked  degree.  This  is  well  seen  in  a  compari- 
son of  deaths  from  certain  infectious  diseases  in  drinkers  and 
abstainers,  the  percentage  of  mortality  being  much  greater  in  the 
former. 

Dr.  T.  Alexander  MacNichol,  in  a  recent  address,  said :  — 

''  Massart  and  Bordet,  Metchnikoff  and  Sims  Woodhead,  have 
proved  that  alcohol,  even  in  very  dilute  solution,  prevents  the 
white  blood  corpuscles  from  attacking  invading  germs,  thus  de- 
priving the  system  of  the  cooperation  of  these  important  defenders, 
and  reducing  the  powers  of  resisting  disease.  The  experiments  of 
Richardson,  Harley,  Kales,  and  others  have  demonstrated  the 
fact  that  one  to  five  per  cent  of  alcohol  in  the  blood  of  the  living 
human  body  in  a  notable  degree  alters  the  appearance  of  the  cor- 
puscular elements,  reduces  the  oxygen  bearing  elements,  and  pre- 
vents their  reoxygenation." 

Alcohol  weakens  Resistance  to. Disease. — ^  In  acute  illnesses, 
grippe,  fevers,  blood  poisoning,  etc.,  substances  formed  in  the 
blood  termed  '^  antibodies  "  antagonize  the  action  of  bacteria, 
facilitating  their  destruction  by  the  white  blood  cells  and  neutral- 
izing their  poisonous  influence.  In  a  person  with  good  ''resist- 
ance" this  protective  machinery,  which  we  do  not  yet  thoroughly 
understand,  works  with  beautiful  precision,  and  the  patient  ''gets 
well."  Experiments  by  scientific  experts  have  demonstrated  that 
alcohol  restrains  the  formation  of  these  marvelous  antibodies. 
Alcohol  puts  to  sleep  the  sentinels  that  guard  your  body  from 
disease. 

The  Effect  of  Alcohol  on  the  Circulation.  —  Alcoholic  drinks 
affect  the  very  delicate  adjustment  of  the  nervous  centers  control- 


328  THE   BLOOD  AND   ITS   CIRCULATION 

ling  the  blood  vessels  and  heart.  Even  very  dilute  alcohol  acts 
upon  the  muscles  of  the  tiny  blood  vessels ;  consequently,  more 
blood  is  allowed  to  enter  them,  and,  as  the  small  vessels  are  usually 
near  the  surface  of  the  body,  the  habitual  redness  seen  in  the  face 
of  hard  drinkers  is  the  ultimate  result. 

^'  The  first  effect  of  diluted  alcohol  is  to  make  the  heart  beat 
faster.  This  fills  the  small  vessels  near  the  surface.  A  feeling  of 
warmth  is  produced  which  causes  the  drinker  to  feel  that  he  was 
warmed  by  the  drink.  This  feeling,  however,  soon  passes  away, 
and  is  succeeded  by  one  of  chilliness.  The  body  temperature,  at 
first  raised  by  the  rather  rapid  oxidation  of  the  alcohol,  is  soon 
lowered  by  the  increased  radiation  from  the  surface. 

"  The  immediate  stimulation  to  the  heart's  action  soon  passes 
away  and,  like  other  muscles,  the  muscles  of  the  heart  lose  power 
and  contract  with  less  force  after  having  been  excited  by  alcohol." 
—  Macy,  Physiology. 

Alcohol,  when  brought  to  act  directly  on  heart  muscle,  lessens  the 
force  of  the  beat.  It  may  even  cause  changes  in  the  tissues,  which 
eventually  result  in  the  breaking  of  the  walls  of  a  blood  vessel  or 
the  plugging  of  a  vessel  with  a  blood  clot.  This  condition  may 
cause  the  disease  known  as  apoplexy. 

Effects  of  Tobacco  upon  the  Circulation.  —  "  The  frequent  use  of 
cigars  or  cigarettes  by  the  young  seriously  affects  the  quality  of  the 
blood.  The  red  blood  corpuscles  are  not  fully  developed  and 
charged  with  their  normal  supply  of  life-giving  oxygen.  This 
causes  paleness  of  the  skin,  often  noticed  in  the  face  of  the  young 
smoker.  Palpitation  of  the  heart  is  also  a  common  result,  fol- 
lowed by  permanent  weakness,  so  that  the  whole  system  is 
enfeebled,  and  mental  vigor  is  impaired  as  well  as  physical 
strength."  —  Macy,  Physiology. 


XXII.     RESPIRATION   AND   EXCRETION 

Problems, — A  study  of  respiration  to  find  out:  — 
{a)    What  changes  in  blood  and  air  take  place  within  the 
lungs. 
(b)    The  mechanics  of  respiration. 
A  study  of  ventilation  to  discover :  — 
{a)  The  reason  for  ventilation, 
(b)    The  best  method  of  ventilation. 
A  study  of  the  organs  of  excretion. 

Laboratory  Suggestions 

Demonstration.  —  Comparison  of  lungs  of  frog  with  those  of  bird  or 
mammal. 

Experiment.  —  The  changes  of  blood  within  the  lungS. 

Experiment.  —  Changes  taking  place  in  air  in  the  lungs. 

Experiment.  —  The  use  of  the  ribs  in  respiration. 

Demonstration  experiment.  —  What  causes  the  filling  of  air  sacs  of  the 
lungs  ? 

Demonstration  experiment.  —  What  are  the  best  methods  of  ventilating 
a  room  ? 

Demonstration.  —  Best  methods  of  dusting  and  cleaning. 

Demonstration.  —  Beef  or  sheep's  kidney  to  show  areas. 

Necessity  for  Respiration.  —  We  have  seen  that  plants  and 
animals  need  oxygen  in  order  that  the  life  processes  may  go  on. 
Food  is  oxidized  to  release  energy,  just  as  coal  is  burned  to  give 
heat  to  run  an  engine.  As  a  draft  of  air  is  required  to  make  fire 
under  the  boiler,  so,  in  the  human  body,  oxygen  must  be  given  so 
that  food  in  tissues  may  be  oxidized  to  release  energy  used  in 
work.  This  oxidation  takes  place  in  the  cells  of  the  body,  be  they 
part  of  a  muscle,  a  gland,  or  the  brain.  Blood,  in  its  circulation 
to  all  parts  of  the  body,  is  the  medium  ivhich  conveys  the  oxygen  to 
that  place  in  the  body  where  it  will  be  used. 

329 


330 


RESPIRATION  AND   EXCRETION 


The  Organs  of  Respiration  in  Man.  —  We  have  alluded  to 
the  fact  that  the  lungs  are  the  organs  which  give  oxygen  to  the 
blood  and  take  from  it  carbon  dioxide.  The  course  of  the  air 
passing  to  the  lungs  in  man  is  much  the  same  as  in  the 
frog.  Air  passes  through  the  nose,  and  into  the  windpipe.  This 
cartilaginous  tube,  the  top  of  which  may  easily  be  felt  as  the 
Adam's  apple  of  the  throat,  divides  into  two  bronchi.  The 
bronchi  within  the  lungs  break  up  into  a  great  number  of  smaller 
tubes,  the  bronchial  tubes,  which  divide  somewhat  like  the  small 

branches  of  a  tree.  The 
bronchial  tubes,  indeed  all 
the  air  passages,  are  lined 
with  ciliated  cells.  The 
cilia  of  these  cells  are  con- 
stantly in  motion,  beating 
with  a  quick  stroke  toward 
the  outer  end  of  the  tube, 
that  is,  toward  the  mouth. 
Hence  any  foreign  material 
will  be  raised  from  the 
throat  first  by  the  action 
of  the  cilia  and  then  by 
coughing  or  "  clearing  the 
throat."  The  bronchi  end 
in  very  minute  air  sacs, 
little  pouches  having  elastic  walls,  into  which  air  is  taken  when 
we  inspire,  or  take  a  deep  breath.  In  the  walls  of  these  pouches 
are  numerous  capillaries,  the  ends  of  arteries  which  pass  from  the 
heart  into  the  lung.  It  is  through  the  very  thin  walls  of  the  air  sacs 
that  an  interchange  of  gases  takes  place  which  results  in  the  blood 
giving  up  part  of  its  load  of  carbon  dioxide,  and  taking  up  oxygen  in 
its  place.  This  exchange  appears  to  be  aided  by  the  presence 
of  an  enzyme  in  the  lung  tissues.  This  is  another  example  of 
the  various  kinds  of  work  done  by  the  enzymes  of  the  body. 

Changes  in  the  Blood  within  the  Lungs.  —  Blood,  after  leaving 
the  lungs,  is  much  brighter  red  than  just  before  entering  them. 
The  change  in  color  is  due  to  a  taking  up  of  oxygen  by  the  hoBmo- 


Air  passages  in  the  human  lungs,  a,  larynx ; 
6,  trachea  (or  windpipe)  ;  c,  d,  bronchi ; 
e,  bronchial  tubes ;  /,  cluster  of  air  cells. 


RESPIRATION  AND    EXCRETION 


331 


glohin  of  the  red  corpuscles.  Changes  taking  place  in  blood  are 
obviously  the  reverse  of  those  which  take  place  in  air  in  the 
lungs.  Every  hundred  cubic  centimeters  of  blood  going  into 
the  lungs  contains  8  to  12  c.c.  -c      ^    ■, 

JjToncmal 

of   oxygen,  45   to    50    c.c.   of  Tixbe 

carbon  dioxide,  and  1  to  2  c.c. 


rroYn. 


^      Jo 
piumonary 


Diagram  to  show  what  the  blood  loses  and 
gains  in  one  of  the  air  sacs  of  the  lungs. 


of  nitrogen.    The  same  amount    fi^'^nonaTy 

artery 

of  blood  passing  out  of  the 
lungs  contains  20  c.c.  of  oxy- 
gen, 38  c.c.  of  carbon  dioxide, 
and  1  to  2  c.c.  of  nitrogen. 
The  water,  of  which  about 
half  a  pint  is  given  off  daily, 
is  mostlj^  lost  from  the  blood. 

Changes  in  Air  in  the  Lungs. 
—  Air  is  much  warmer  after 
leaving  the  lungs  than  before 
it  enters  them.  Breathe  on 
the  bulb  of  a  thermometer  to 
prove  this.  Expired  air  con- 
tains a  considerable  amount 
of  moisture,  as  may  be  proved  by  breathing  on  a  cold  polished 
surface.  This  it  has  taken  up  in  the  air  sacs  of  the  lungs.  The 
presence  of  carbon  dioxide  in  expired  air  may  easily  be  detected 
bv  the  limewater  test.  Air  such  as  we  breathe  out  of  doors  con- 
tains,  by  volume  :  — 

Nitrogen       76.95 

Oxygen .     20.61 

Carbon  dioxide 03 

Argon 1.00 

Water  vapor  (average) 1.40 

Air  expired  from  the  lungs  contains  :  — 

Nitrogen       76.95 

Oxygen 15.67 

Carbon  dioxide 4.38 

Water  vapor 2 

Argon       1 


332 


RESPIRATION  AND  EXCRETION 


In  other  words,  there  is  a  loss  between  4  and  5  per  cent  oxygen, 
and  nearly  a  corresponding  gain  in  carbon  dioxide,  in  expired  air. 
There  are  also  some  other  organic  substances  present. 

Cell  Respiration.  —  It  has  been  shown,  in  the  case  of  very 
simple  animals,  such  as  the  amceba,  that  when  oxidation  takes 
place  in  a  cell,  work  results  from  this  oxidation.  The  oxygen 
taken  into  the  lungs  is  not  used  there,  but  is  carried  by  the  blood 
to  such  parts  of  the  body  as  need  oxygen  to  oxidize  food  mate- 
rials in  the  cells.  Since 
work  is  done  in  the  cells 
of  the  body,  food  and  oxy- 
gen are  therefore  required. 
The  quantity  of  oxygen 
used  by  the  body  is  nearly 
dependent  on  the  amount 
of  work  performed.  Oxy- 
gen is  constantly  taken 
from  the  blood  by  tissues 
in  a  state  of  rest  and  is 
used  up  when  the  body  is 
at  work.  This  is  suggested 
by  the  fact  that  in  a  given 
time  a  man,  when  working,  gives  off  more  oxygen  (in  carbon 
dioxide)  than  he  takes  in  during  that  time. 

While  work  is  being  done  certain  wastes  are  formed  in  the  cell. 
Carbon  dioxide  is  given  off  when  carbon  is  burned.  But  when 
proteins  are  burned,  another  waste  product  containing  nitrogen 
is  formed.  This  must  be  passed  off  from  the  cells,  as  it  is  a  poison. 
Here  again  the  lymph  and  blood,  the  common  carriers,  take  the 
waste  material  to  points  where  it  may  be  excreted  or  passed  out  of 
the  body. 

The  Mechanics  of  Respiration.  The  Pleura.  —  The  lungs  are 
covered  with  a  thin  elastic  membrane,  the  pleura.  This  forms  a 
bag  in  which  the  lungs  are  hung.  Between  the  walls  of  the  bag 
and  the  lungs  is  a  space  filled  with  lymph.  By  this  means 
the  lungs  are  prevented  from  rubbing  against  the  walls  of  the 
chest. 


The  respiration  of  cells. 


RESPIRATION  AND   EXCRETION 


333 


diaphragm] 


Breathing.  —  In  every 
Ml  breath  there  are  two 
distinct  movements,  in- 
spiration (taking  air  in) 
and  expiration  (forcing 
air  out) .  In  man  an  in- 
spiration is  produced  by 
the  contraction  of  the 
muscles  between  the  diaphragm 
ribs,  together  with  the 
contraction  of  the  dia- 
phragm, the  muscular 
wall  just  below  the  heart  ^^Xf'^t  ""^^'^^  ^""^  ^^^^^  ^'"^^^^  f  Ml  breath ; 

••  ,  {o),    alter   an    expiration.         Explain    now    the 

and   lungs  ;     this    results         cavity  for  lungs  is  made  larger. 

in  pulling  down  the  dia- 
phragm and  pulling  upward  and  outward  of  the  ribs,  thus  making 
the  space  within  the  chest  cavity  larger.     The  lungs,  which  lie 

within  this  cavity,  are  filled  by 
the  air  rushing  into  the  larger 
space  thus  made.  That  this 
cavity  is  larger  than  it  was  at 
first  may  be  demonstrated  by  a 
glance  at  the  accompanying 
figure.  An  expiration  is  simpler 
than  an  inspiration,  for  it  re- 
quires no  muscular  effort ;  the 
muscles  relax,  the  breastbone 
and  ribs  sink  into  place,  while 
the  diaphragm  returns  to  its 
original  position. 

A  piece  of  apparatus  which  illus- 
trates to  a  degree  the  mechanics  of 
breathing  may  be  made  as  follows : 
Attach  a  string  to  the  middle  of  a 
piece  of  sheet  rubber.  Tie  the 
rubber  over  the  large  end  of  a  bell 
jar.    Pass  a  glass  Y-tube  through  a 


Apparatus  to  show  the  mechanics  of 
breathing. 


334 


RESPIRATION  AND  EXCRETION 


i^Gomplemcntal 


rubber  stopper.  Fasten  two  small  toy  balloons  to  the  branches  of  the 
tube.  Close  the  small  end  of  the  jar  with  the  stopper.  Adjust  the  tube 
so  that  the  balloons  shall  hang  free  in  the  jar.  If  now  the  rubber  sheet  is 
pulled  down  by  means  of  the  string,  the  air  pressure  in  the  jar  is  reduced 
and  the  toy  balloons  within  expand,  owing  to  the  air  pressure  down  the 
tube.  When  the  rubber  is  allowed  to  go  back  to  its  former  position,  the 
balloons  collapse. 

Rate  of  Breathing  and  Amount  of  Air  Breathed.  —  During  quiet 
breathing,  the  rate  of  inspiration  is  from  fifteen  to  eighteen  times 

per  minute ;  this  rate  largely  depends  on 
the  amount  of  physical  work  performed. 
About  30  cubic  inches  of  air  are  taken  in 
and  expelled  during  the  ordinary  quiet 
respiration.  The  air  so  breathed  is  called 
tidal  air.  In  a  ''long"  breath,  we  take 
in  about  100  cubic  inches  in  addition  to 
the  tidal  air.  This  is  called  complemental 
air.  By  means  of  a  forced  expiration,  it 
is  possible  to  expel  from  75  to  100  cubic 
inches  more  than  tidal  air ;  this  air  is 
called  reserve  air.  What  remains  in  the 
lungs,  amounting  to  about  100  cubic 
inches,  is  called  the  residual  air.  The 
value  of  deep  breathing  is  seen  by  a 
glance  at  the  diagram.  It  is  only  by 
this  means  that  we  clear  the  lungs  of  the 
reserve  air  with  its  accompanying  load  of 
carbon  dioxide. 


Tidal  Air 
30  cu.  in. 


TAir= 
WfCFO^cii=ir^ 


230 
cu.  in. 


Respiration  under  Nervous  Control.  —  The 

muscular  movements  which  cause  an  inspira- 


Diagram  showing  the  relative 
amounts  of  tidal,  comple- 
mental, reserve,  and  resid- 
ual air.     The  brace  shows    ^.  ,,  i        ,,  ,      ^      c  l^  -n 
the  average  lung  capacity    ^lon  are  partly  under  the  control  of  the  will, 

for  the  adult  man.  but  in  part  the  movement  is  beyond  our  con- 

trol. The  nerve  centers  which  govern  in- 
spiration are  part  of  the  sympathetic  nervous  system.  Anything  of 
an  irritating  nature  in  the  trachea  or  larynx  will  cause  a  sudden  expiration 
or  cough.  When  a  boy  runs,  the  quickened  respiration  is  due  to  the  fact 
that  oxygen  is  used  up  rapidly  and  a  larger  quantity  of  carbon  dioxide  is 


RESPIRATION   AND   EXCRETION 


335 


formed.  The  carbon  dioxide  in  the  blood  stimulates  the  nervous  center 
which  has  control  of  respiration  to  greater  activity,  and  quickened  inspira- 
tion follows. 


Need  of  Ventilation.  —  During  the  course  of  a  day  the  lungs 
lose  to  the  surrounding  air  nearly  two  pounds  of  carbon  diox- 
ide. This  means  that  about  three  fifths  of  a  cubic  foot  is  given 
off  by  each  person  during  an  hour.  When  we  are  confined  for 
some  time  in  a  room,  it  becomes  necessary  to  get  rid  of  this 
carbon  dioxide.  This  can  be  done  only  by  means  of  proper 
ventilation.  A  considerable  amount  of  moisture  is  given  off  from 
the  body,  and  this  moisture  in  a  crowded  room  is  responsible  for 
much  of  the  discomfort.  The  air  becomes  humid  and  uncomfort- 
able.    It  has  been  found  that  by  keeping  the  air  in  motion  in  such 


O  I-,'.'.  V_l?!rl---Iv}  :  1  :t '  -  ^  J  i 


■-  -it~'  -' 


—  _.  -^      ^ 


a 


o 


a  room  (as  through  the  use  of  electric 
fans)  much  of  this  discomfort  is 
obviated. 

The  presence  of  impurities  in  the 
air  of  a  room  may  easily  be  deter- 
mined by  its  odor.  The  odor  of  a 
poorly  ventilated  room  is  due  to 
organic  impurities  given  off  with  the 
carbon  dioxide.  This,  fortunately, 
gives  us  an  index  of  the  amount  of 
waste  material  in  the  air.  Among 
the  factors  which  take  oxygen  from 
the  air  in  a  closed  room  and  produce 
carbon  dioxide  are  burning  gas  or  oil 
lamps  and  stoves,  and  the  presence 
of  a  number  of  people. 

Proper  Ventilation.  —  Ventilation 
consists  in  the  removal  of  air  that 
has  been  used,  and  the  introduction 
of  a  fresh  supply  to  take  its  place. 

Heated    air    rises,    carrying    with    it     Three  ways  of  ventilating  a  room. 

much   of    the    carbon   dioxide    and      WS  tttV  brrt'^dt, 

other    impurities.      A    good    method        ventilation?     Explain. 


] 


o 


.'. '*-  ------i^---- 


1 


336 


RESPIRATION  AND   EXCRETION 


of  ventilation  for  the  home  is  to  place  a  board  two  or  three 
inches  high  between  the  lower  sash  and  the  frame  of  a  window 
or  to  have  the  window  open  an  inch  or  so  at  the  top  and  the 
bottom.  An  open  fireplace  in  a  room  aids  in  ventilation  because 
of  the  constant  draft  up  the  fine. 

Sweeping  and  Dusting.  —  It  is  very  easy  to  demonstrate  the 
amount  of  dust  in  the  air  by  following  the  course  of  a  beam  of 
light  in  a  darkened  room.     We  have  already  proved  that  spores  of 

mold  and  yeast  exist  in 
the  air.  That  bacteria 
are  also  present  can  be 
proved  by  exposing  a 
sterilized  gelatin  plate 
to  the  air  in  a  school- 
room for  a  few  mo- 
ments.^ 

Many  of  the  bacteria 
present  in  the  air  are 
active  in  causing  dis- 
eases of  the  respiratory 
tract,  such  as  diph- 
theria, membranous 
croup,  and  tubercu- 
losis. Other  diseases, 
as  colds,  bronchitis 
(inflammation  of  the 
bronchial  tubes),  and 
pneumonia  (inflammation  of  the  tiny  air  sacs  of  the  lungs),  are 
also  caused  by  bacteria. 

Dust,  with  its  load  of  bacteria,  will  settle  on  any  horizontal  sur 
face  in  a  room  not  used  for  three  or  four  hours.     Dusting  and 
sweeping  should  always  be  done  with  a  damp  cloth  or  broom, 
otherwise  the  bacteria  are  simply  stirred  up  and  sent  into  the  air 


Plate  culture  exposed  for  five  minutes  in  a  school 
hall  where  pupils  were  passing  to  recitations. 
Each  spot  is  a  colony  of  bacteria  or  mold. 


i 


^  Expose  two  sterilized  dishes  containing  culture  media ;  one  in  a  room  being 
swept  with  a  damp  broom,  and  the  other  in  a  room  which  is  being  swept  in  the  usual 
manner.  Note  the  formation  of  colonies  of  bacteria  in  each  dish.  In  which  dish 
does  the  more  abundant  growth  take  place  ? 


RESPIRATION  AND   EXCRETION 


337 


again.  The  proper  watering  of  streets  before  they  are  swept  is 
also  an  important  factor  in  health.  Much  dust  is  composed  largely 
of  dried  excreta  of  animals.  Soft-coal  smoke  does  its  share  to 
add  to  the  impurities  of  the  air,  while  sewer  gas  and  illuminating 
gas  are  frequently  found  in  sufficient  quantities  to  poison  people. 
Pure  air  is,  as  can  be  seen,  almost  an  impossibility  in  a  great  city. 

How  to  get  Fresh  Air.  —  As  we  know,  green  plants  give  off  in 
the  sunlight  considerable  more  oxygen  than  they  use,  and  they 
use  up  carbon  dioxide.  The  air  in  the  country  is  naturally  purer 
than  in  the  city,  as  smoke  and  bacteria  are  not  so  prevalent  there, 
and  the  plants  ill  abundance  give  off  oxygen.  In  the  city  the 
night  air  is  purer  than  day  air, 
because  the  factories  have  stopped 
work,  the  dust  has  settled,  and 
fewer  people  arc  on  the  streets. 
The  old  myth  of  "  night  air " 
being  injurious  has  long  since  been 
exploded,  and  thousands  of  people 
of  delicate  health,  especially  those 
who  have  weak  throat  or  lungs, 
are  regaining  health  by  sleeping 
out  of  doors  or  with  the  windows 
wide  open.  The  only  essential  in 
sleeping  out  of  doors  or  in  a  room 
with  a  low  temperature  is  that  the  body  be  kept  warm  and  the 
head  be  protected  from  strong  drafts  by  a  nightcap  or  hood. 
Proper  ventilation  at  all  times  is  one  of  the  greatest  factors  in 
good  health. 

Change  of  Air.  —  Persons  in  poor  health,  especially  those  having 
tuberculosis,  are  often  cured  by  a  change  of  air.  This  is  not  always 
so  much  due  to  the  composition  of  the  air  as  to  change  of  occupa- 
tion, rest,  and  good  food.  Mountain  air  is  dry,  and  relatively 
free  from  dust  and  bacteria,  and  often  helps  a  person  having  tuber- 
culosis. Air  at  the  seaside  is  beneficial  for  some  forms  of  disease, 
especially  hay  fever  and  bone  tuberculosis.  Many  sanitariums 
have  been  established  for  this  latter  disease  near  the  ocean,  and 
thousands  of  lives  are  being  annually  saved  in  this  way. 

HUNTER,    CIV.    BI. 22 


A  sleeping  porch,  an  ideal  way  to 
get  fresh  air  at  night. 


338 


RESPIRATION   AND   EXCRETION 


Ventilation  of  Sleeping  Rooms.  —  Sleeping  in  close  rooms  is 
the  cause  of  much  illness.  Beds  ought  to  be  placed  so  that  a 
constant  supply  of  fresh  air  is  given  without  a  direct  draft.  This 
may  often  be  managed  with  the  use  of  screens.  Bedroom  windows 
should  be  thrown  open  in  the  morning  to  allow  free  entrance  of  the 
sun  and  air,  bedclothes  should  be  washed  frequently,  and  sheets 


Unfavorable  sleeping  conditions.     Explain  why  unfavorable. 

and  pillow  covers  often  changed.     Bedroom  furniture  should  be 
simple,  and  but  little  drapery  allowed  in  the  room. 

Hygienic  Habits  of  Breathing.  —  Every  one  ought  to  accustom 
himself  upon  going  into  the  open  air  to  inspire  slowly  and  deeply 
to  the  full  capacity  of  the  lungs.  A  slow  expiration  should  follow. 
Take  care  to  force  the  air  out.  Breathe  through  the  nose,  thus 
warming  the  air  you  inspire  before  it  enters  the  lungs  and  chills 
the  blood.  Repeat  this  exercise  several  times  every  day.  You 
will  thus  prevent  certain  of  the  air  sacs  which  are  not  often  used 
from  becoming  hardened  and  permanently  closed. 


RESPIRATION   AND   EXCRETION  339 

Relation  of  Proper  Exercise  to  Health.  —  We  are  all  aware  that 
exercise  in  moderation  has  a  beneficial  effect  upon  the  human  or- 
ganism. The  pale  face,  drooping  shoulders,  and  narrow  chest  of 
the  boy  or  girl  who  takes  no  regular  exercise  is  too  well  known. 
Exercise,  besides  giving  direct  use  of  the  muscles,  increases  the 
work  of  the  heart  and  lungs,  causing  deeper  breathing  and  giving 
the  heart  muscles  increased  work;  it  liberates  heat  and  carbon 
dioxide  from  the  tissues  where  the  work  is  taking  place,  thus  in- 
creasing the  respiration  of  the  tissues  themselves,  and  aids  me- 
chanically in  the  removal  of  wastes  from  tissues.  It  is  well  known 
that  exercise,  when  taken  some  little  time  after  eating,  has  a  very 
beneficial  effect  upon  digestion.  Exercise  and  especially  games 
are  of  immense  importance  to  the  nervous  system  as  a  means  of 
rest.  The  increasing  number  of  playgrounds  in  this  country  is 
due  to  this  acknowledged  need  of  exercise,  especially  for  growing 
children. 

Proper  exercise  should  be  moderate  and  varied.  Walking  in 
itself  is  a  valuable  means  of  exercising  certain  muscles,  so  is  bicy- 
cling, but  neither  is  ideal  as  the  only  form  to  be  used.  Vary  your 
exercise  so  as  to  bring  different  muscles  into  play,  take  exercise 
that  will  allow  free  breathing  out  of  doors  if  possible,  and  the 
natural  fatigue  which  follows  will  lead  you  to  take  the  rest  and  sleep 
that  every  normal  body  requires. 

Exercise  should  always  be  limited  by  fatigue,  which  brings  with 
it  fatigue  poisons.  This  is  nature's  signal  when  to  rest.  If  one's 
use  of  diet  and  air  is  proper,  the  fatigue  point  will  be  much  further 
off  than  otherwise.  One  should  learn  to  relax  when  not  in  activity. 
The  habit  produces  rest,  even  between  exertions  very  close  to- 
gether, and  enables  one  to  continue  to  repeat  those  exertions  for 
a  much  longer  time  than  otherwise.  The  habit  of  lying  down 
when  tired  is  a  good  one. 

The  Relation  of  Tight  Clothing  to  Correct  Breathing.  —  It  is 
impossible  to  breathe  correctly  unless  the  clothing  is  worn  loosely 
over  the  chest  and  abdomen.  Tight  corsets  and  tight  belts  pre- 
vent the  walls  of  the  chest  and  the  abdomen  from  pushing  outward 
and  interfere  with  the  drawing  of  air  into  the  lungs.  They  may 
also  result  in  permanent  distortion  of  parts  of  the  skeleton  directly 


340  RESPIRATION  AND   EXCRETION 

under  the  pressure.  Other  organs  of  the  body  cavity,  as  the  stom- 
ach and  intestines,  may  be  forced  downward,  out  of  place,  and  in 
consequence  cannot  perform  their  work  properly. 

Suffocation  and  Artificial  Respiration.  —  Suffocation  results  from  the 
shutting  off  of  the  supply  of  oxygen  from  the  lungs.  It  may  be  brought 
about  by  an  obstruction  in  the  windpipe,  by  a  lack  of  oxygen  in  the  air, 
by  inhaling  some  other  gas  in  quantity,  or  by  drowning.  A  severe  electric 
shock  may  paralyze  the  nervous  centers  which  control  respiration,  thus 
causing  a  kind  of  suffocation.  In  the  above  cases,  death  often  may  be 
prevented  by  prompt  recourse  to  artificial  respiration.  To  accomplish 
this,  place  the  patient  on  his  back  with  the  head  lower  than  the  body; 
grasp  the  arms  near  the  elbows  and  draw  them,  upward  and  outward  until 
they  are  stretched  above  the  head,  on  a  line  with  the  body.  By  this  means 
the  chest  cavity  is  enlarged  and  an  inspiration  produced.  To  produce 
an  expiration,  carry  the  anns  downward,  and  press  them  against  the  chest, 
thus  forcing  the  air  cut  of  the  lungs.  This  exercise,  regularly  repeated 
every  few  seconds,  if  necessary  for  hours,  has  been  the  source  of  saving 
many  lives.  • 

Common  Diseases  of  the  Nose  and  Throat.  —  Catarrh  is  a  disease  to 
which  people  with  sensitive  mucous  membrane  of  the  nose  and  throat  are 
subject.  It  is  indicated  by  the  constant  secretion  of  mucus  from  these 
membranes.  Frequent  spraying  of  the  nose  and  throat  with  some  mild 
antiseptic  solutions  is  found  helpful.  Chronic  catarrh  should  be  attended 
to  bj^  a  physician.  Often  we  find  children  breathing  entirely  through  the 
mouth,  the  nose  being  seemingly  stopped  up.  When  this  goes  on  for 
some  time  the  nose  and  throat  should  be  examined  by  a  physician  for 
adenoids,  or  growths  of  soft  masses  of  tissue  which  fill  up  the  nose  cavity, 
thus  causing  a  shortage  of  the  air  supply  for  the  body.  Many  a  child, 
backward  at  school,  thin  and  irritable,  has  been  changed  to  a  healthy, 
normal,  bright  scholar  by  the  removal  of  adenoids.  Sometimes  the 
tonsils  at  the  back  of  the  mouth  cavity  may  become  enlarged,  thus  shut- 
ting off  the  air  supply  and  causing  the  same  trouble  as  we  see  in  a  case  of 
adenoids.  The  simple  removal  of  the  obstacle  by  a  doctor  soon  cures 
this  condition.     (See  page  395.) 

Organs  of  Excretion.  —  All  the  life  processes  which  take  place 
in  a  living  thing  result  ultimately,  in  addition  to  giving  off  of  car- 
bon dioxide,  in  the  formation  of  organic  wastes  within  the  body. 
The  retention  of  these  wastes  which  contain  nitrogen,  is  harmful 


RESPIRATION  AND  EXCRETION 


341 


—  Suprarenal 
body 

—Cortex 

—-Medulla 

i^Pyramids 


-  Pelvis 


-  Ureter 


Longitudinal  section  through  a 
kidney. 


to  animals.     In  man,  the  skin  and 

kidneys   remove    this  waste    from 

the  body,  hence  they  are  called  the 

organs  of  excretion. 

The       Human      Kidney.  —  The 

human  kidney  is  about  four  inches 

long,  two  and  one  half  inches  wide, 

and   one  inch    in    thickness.      Its 

color  is  dark  red.     If  the  structure 

of    the    medulla    and    cortex    (see 

figure    above)   is  examined    under 

the  compound  microscope,  you  will 

find  these  regions  to  be  composed 

of  a  vast  number  of  tiny  branched 

and   twisted   tubules.      The  outer 

end  of  each  of  these  tubules  opens  into  the  pelvis,  the  space  within 

the  kidney ;  the  inner  end,  in  the  cortex,  forms  a  tiny  closed  sac. 

In  each  sac,  the  outer  wall  of  the  tube  has  grown  inward  and 

carried  with  it  a  very  tiny  artery.  This 
artery  breaks  up  into  a  mass  of  capillaries. 
These  capillaries,  in  turn,  unite  to  form  a 
small  vein  as  they  leave  the  little  sac. 
Each  of  these  sacs  with  its  contained  blood 
vessels  is  called  a  glomerulus. 

Wastes  given  off  by  the  Blood  in  the 
Kidney.  —  In  the  glomerulus  the  blood 
loses  by  osmosis,  through  the  very  thin 
walls  of  the  capillaries,  first,  a  consider- 
able amount  of  water  (amounting  to 
nearly  three  pints  daily)  ;  second,  a  nitrog- 
enous  waste    material    known   as    urea; 

°«f:".hll;f :Vr™:   third,  salts  and  other  waste  organic  sub- 
lus  and  tubule:  a,  artery    stanccs,  uric  acid  among  them. 

bringing    blood    to    part ; 

h,  capillary  bringing  blood        These  waste   products,  together  with  the 

to  glomerulus;  h',  vessel    -^ater  containing  them,  are   known  as  urine. 
continuing  with  blood  to    „,      ,    ,    ,  ,     e     • ,  x     i        • 

vein ;  c,  vein ;  t,  tubule ;    The  total  amount  01  nitrogenous  waste  leavmg 

G,  glomerulus.  the  body  each  day  is  about  twenty  grams.     It 


342 


RESPIRATION  AND  EXCRETION 


is  passed  through  the  ureter  to  the  urinanj  bladder;  from  this  reservoir 
it  is  passed  out  of  the  body,  through  a  tube  called  the  urethra.  After 
the  blood  has  passed  through  the  glomeruli  of  the  kidneys  it  is  purer 
than  in  any  other  place  in  the  body,  because,  before  coming  there,  it 
lost  a  large  part  of  its  burden  of  carbon  dioxide  in  the  lungs.  After 
leaving  the  kidney  it  has  lost  much  of  its  nitrogenous  waste.  So  de- 
pendent is  the  body  upon  the  excretion  of  its  poisonous  material  that, 
in  cases  where  the  kidneys  do  not  do  their  work  properly,  death  may 
ensue  within  a  few  hours. 

Structure   and   Use   of   Sweat   Glands.  —  If  you   examine  the 
palm  of  your  hand  with  a  lens,  you  will  notice  the  surface  is  thrown 


Sweatiytict 

Uomy  layer 
Figment  layer  i  [M^ 


Sebaceous  Gland 


Tactile  Organs^ 
Nerve—" 
Blood  Vessels - 

Sweat  Gland-'Jl^- 
Fat 


>  Epiderm.13 


)  Dermis 


Subcutaneous  layer  of 
'  connective  tissue  and  fat 


Diagram  of  a  section  of  the  skin.     (Highly  magnified.) 

into  little  ridges.  In  these  ridges  may  be  found  a  large  number  of 
very  tiny  pits ;  these  are  the  pores  or  openings  of  the  sweat- 
secreting  glands.  From  each  opening  a  little  tube  penetrates  deep 
within  the  epidermis;  there,  coiling  around  upon  itself  several 
times,  it  forms  the  sweat  gland.  Close  around  this  coiled  tube  are 
found  many  capillaries.  From  the  blood  in  these  capillaries,  cells 
lining  the  wall  of  the  gland  take  water,  and  with  it  a  little  carbon 
dioxide,  urea,  and  some  salts  (common  salt  among  others).  This 
forms  the  excretion  known  as  sweat.  The  combined  secretions 
from  these  glands  amount  normally  to  a  little  over  a  pint  during 


RESPIRATION  AND  EXCRETION  343 

twenty-four  hours.  At  all  times,  a  small  amount  of  sweat  is  given 
off,  but  this  is  evaporated  or  is  absorbed  by  the  underwear ;  as 
this  passes  off  unnoticed,  it  is  called  insensible  perspiration.  In 
hot  weather  or  after  hard  manual  labor  the  amount  of  perspira- 
tion is  greatly  increased. 

Regulation  of  Heat  of  the  Body.  —  The  bodily  temperature 
of  a  person  engaged  in  manual  labor  will  be  found  to  be  but  little 
higher  than  the  temperature  of  the  same  person  at  rest.  We  know 
from  our  previous  experiments  that  heat  is  released.  Muscles, 
nearly  one  half  the  weight  of  the  body,  release  about  five  sixths  of 
their  energy  as  heat.  At  all  times  they  are  giving  up  some  heat. 
How  is  it  that  the  bodily  temperature  does  not  differ  greatly  at 
such  times  ?  The  temperature  of  the  body  is  largely  regulated  by 
means  of  the  activity  of  the  sweat  glands.  The  blood  carries 
much  of  the  heat,  liberated  in  the  various  parts  of  the  body  by 
the  oxidation  of  food,  to  the  surface  of  the  body,  where  it  is  lost 
in  the  evaporation  of  sweat.  In  hot  weather  the  blood  vessels  of 
the  skin  are  dilated ;  in  cold  weather  they  are  made  smaller  by 
the  action  of  the  nervous  system.  The  blood  thus  loses  water  in 
the  skin,  the  water  evaporates,  and  we  are  cooled  off.  The  object 
of  increased  perspiration,  then,  is  to  remove  heat  from  the  body. 
With  a  large  amount  of  blood  present  in  the  skin,  perspiration  is 
increased ;  with  a  small  amount,  it  is  diminished.  Hence,  we 
have  in  the  skin  an  automatic  regulator  of  bodily  temperature. 

Sweat  Glands  under  Nervous  Control.  —  The  sweat  glands, 
like  the  other  glands  in  the  body,  are  under  the  control  of  the  sj^m- 
pathetic  nervous  system.  Frequently  the  nerves  dilate  the  blood 
vessels  of  the  skin,  thus  helping  the  sweat  glands  to  secrete,  by 
giving  them  more  blood. 

"  Thus  regulation  is  carried  out  by  the  nervous  system  deter- 
mining, on  the  one  hand,  the  loss  by  governing  the  supply  of  blood 
to  the  skin  and  the  action  of  the  sweat  glands ;  and  on  the  other, 
the  production  by  diminishing  or  increasing  the  oxidation  of  the 
tissues."  —  Foster  and  Shore,    Physiology. 

Colds  and  Fevers.  —  The  regulation  of  blood  passing  through 
the  blood  vessels  is  under  control  of  the  nervous  system.  If  this 
mechanism  is  interfered  with  in  any  way,  the  sweat  glands  may  not 


344 


RESPIRATION  AND   EXCRETION 


.^o 


do  their  work,  perspiration  may  be  stopped,  and  the  heat  from 
oxidation  held  within  the  body.  The  body  temperature  goes  up, 
and  a  fever  results. 

If  the  blood  vessels  in  the  skin  are  suddenly  cooled  when  full  of 
blood,  they  contract  and  send  the  blood  elsewhere.     As  a  result  a 

congestion  or  cold  may  follow. 
Colds  are,  in  reality,  a  conges- 
tion of  membranes  lining  cer- 
tain parts  of  the  body,  as  the 
nose,  throat,  windpipe,  or 
lungs. 

When  suffering  from  a  cold, 
it  is  therefore  important  not 
to  chill  the  skin,  as  a  full  blood 
supply  should  be  kept  in  it  and 
so  kept  from  the  seat  of  the 
congestion.  For  this  reason 
hot  baths  (which  call  the 
blood  to  the  skin),  the  avoid- 
ing of  drafts  (which  chill  the 
skin),  and  warm  clothing  are 
useful  factors  in  the  care  of 
colds. 

Hygiene  of  the  Skin.  —  The 
skin  is  of  importance  both  as 
an  organ  of  excretion  and  as 
a  regulator  of  bodily  temper- 
ature. The  skin  of  the  entire 
body  should  be  bathed  frequently  so  that  this  function  of  excretion 
may  be  properly  performed.  Pride  in  one's  own  appearance  for- 
bids a  dirty  skin.  For  those  who  can  stand  it,  a  cold  sponge  bath 
is  best.  Soap  should  be  used  daily  on  parts  exposed  to  dirt. 
Exercise  in  the  open  air  is  important  to  all  who  desire  a  good 
complexion.  The  body  should  be  kept  at  an  even  temperature 
by  the  use  of  proper  underclothing.  Wool,  a  poor  conductor 
of  heat,  should  be  used  in  winter,  and  cotton,  which  allows  of  a 
free  escape  of  heat,  in  summer. 


A,  blood  vessels  in  skin  normal ;    B,  when 
congested. 


RESPIRATION   AND   EXCRETION  345 

Cuts,  Bruises,  and  Burns.  —  In  case  the  skin  is  badly  broken, 
it  is  necessary  to  prevent  the  entrance  and  growth  of  bacteria. 
This  may  be  done  by  washing  the  wound  with  weak  antiseptic 
solutions  such  as  3  per  cent  carbolic  acid,  3  per  cent  lysol,  or  per- 
oxide of  hydrogen  (full  strength).  These  solutions  should  be  ap- 
plied immediately.  A  burn  or  scald  should  be  covered  at  once 
with  a  paste  of  baking  soda,  with  olive  oil,  or  with  a  mixture  of 
lime  water  and  linseed  oil.  These  tend  to  lessen  the  pain  by  keep- 
ing out  the  air  and  reducing  the  inflammation. 

Summary  of  Changes  in  Blood  within  the  Body.  —  We  have 
already  seen  that  red  corpuscles  in  the  lungs  lose  part  of  their  load 
of  carbon  dioxide  that  they  have  taken  from  the  tissues,  replacing 
it  with  oxygen.  This  is  accompanied  by  a  change  of  color  from 
purple  (in  blood  which  is  poor  in  oxygen)  to  that  of  bright  red  (in 
richly  oxygenated  blood) .  Other  changes  take  place  in  other  parts 
of  the  body.  In  the  walls  of  the  food  tube,  especially  in  the  small 
intestine,  the  blood  receives  its  load  of  fluid  food.  In  the  muscles 
and  other  working  tissues  the  blood  gives  up  food  and  oxygen, 
receiving  carbon  dioxide  and  organic  waste  in  return.  In  the  liver, 
the  blood  gives  up  its  sugar,  and  the  worn-out  red  corpuscles  which 
break  down  are  removed  (as  they  are  in  the  spleen)  from  the 
circulation.  In  glands,  it  gives  up  materials  used  by  the  gland 
cells  in  their  manufacture  of  secretions.  In  the  kidneys,  it  loses 
water  and  nitrogenous  wastes  (urea).  In  the  skin,  it  also  loses 
some  waste  materials,  salts,  and  water. 

"  The  Effect  of  Alcohol  on  Body  Heat.  —  It  is  usually  believed  that 
'  taking  a  drink  '  when  cold  makes  one  warmer.  But  such  is 
not  the  case.  In  reality  alcohol  lowers  the  temperature  of  the 
body  by  dilating  the  blood  vessels  of  the  skin.  It  does  this 
by  means  of  its  influence  on  the  nervous  system.  It  is,  therefore, 
a  mistake  to  drink  alcoholic  beverages  when  one  is  extremely  cold, 
because  by  means  of  this  more  bodily  heat  is  allowed  to  escape. 

^'  Because  alcohol  is  quickly  oxidized,  and  because  heat  is  pro- 
duced in  the  process,  it  was  long  believed  to  be  of  value  in  main- 
taining the  heat  of  the  body.  A  different  view  now  prevails  as 
the  result  of  much  observation  and  experiment.  Physiologists 
show  by  careful  experiments  that  though  the  temperature  of  the 


346  RESPIRATION  AND   EXCRETION 

body  rises  during  digestion  of  food,  it  is  lowered  for  some  hours 
when  alcohol  is  taken.  The  flush  which  is  felt  upon  the  skin  after 
a  drink  of  wine  or  spirits  is  due  in  part  to  an  increase  of  heat  in 
the  body,  but  also  to  the  paralyzing  effect  of  the  alcohol  upon  the 
capillary  walls,  allowing  them  to  dilate,  and  so  permitting  more  of 
the  warm  blood  of  the  interior  of  the  body  to  reach  the  surface. 
There  it  is  cooled  by  radiation,  and  the  general  temperature  is 
lowered."  —  Macy,  Physiology. 

Effect  of  Alcohol  on  Respiration.  —  Alcohol  tends  to  congest 
the  membrane  of  the  throat  and  lungs.  It  does  this  by  paralyzing 
the  nerves  which  take  care  of  the  tiny  blood  vessels  in  the  walls  of 
the  air  tubes  and  air  sacs.  The  capillaries  become  full  of  blood, 
the  air  spaces  are  lessened,  and  breathing  is  interfered  with.  The 
use  of  alcohol  is  believed  by  many  physicians  to  predispose  a 
person  to  tuberculosis.  Certainly  this  disease  attacks  drinkers 
more  readily  than  those  who  do  not  drink.  Alcohol  interferes 
with  the  respiration  of  the  cells  because  it  is  oxidized  very  quickly 
within  "the  body  as  it  is  quickly  absorbed  and  sent  to  the  cells. 
So  rapid  is  this  oxidation  that  it  interferes  with  the  oxidation  of 
other  substances.  Using  alcohol  has  been  likened  to  burning  kero- 
sene in  a  stove  ;  the  operation  is  a  dangerous  one. 

Effects  of  Tobacco  on  Respiration.  —  Tobacco  smoke  contains 
the  same  kind  of  poisons  as  the  tobacco,  with  other  irritating  sub- 
stances added.  It  is  extremely  irritating  to  the  throat ;  it  often 
causes  a  cough,  and  renders  it  more  liable  to  inflammation.  If 
the  smoke  is  inhaled  more  deeply,  the  vaporized  nicotine  is  still 
more  readily  absorbed  and  may  thus  produce  greater  irritation  in 
the  bronchi  and  lungs.  Cigarettes  are  worse  than  other  forms 
of  tobacco,  for  they  contain  the  same  poisons  with  others  in  addi- 
tion. 

Effect  of  Alcohol  on  the  Kidneys.  —  It  is  said  that  alcohol  is  one 
of  the  greatest  causes  of  disease  in  the  kidneys.  The  forms  of 
disease  known  as  "  fatty  degeneration  of  the  kidney "  and 
"  Bright's  disease  "  are  both  frequently  due  to  this  cause.  The 
kidneys  are  the  most  important  organs  for  the  removal  of  nitrog- 
enous waste. 

Alcohol  unites  more  easily  with  oxygen  than  most  other  food 


RESPIRATION  AND   EXCRETION  347 

materials,  hence  it  takes  away  oxygen  that  would  otherwise  be 
used  in  oxidizing  these  foods.  Imperfect  oxidation  of  foods 
causes  the  development  and  retention  of  poisons  in  the  blood 
which  it  becomes  the  work  of  the  kidneys  to  remove.  If  the  kid- 
neys become  overworked,  disease  will  occur.  Such  disease  is  likely 
to  make  itself  felt  as  rheumatism  or  gout,  both  of  which  are  be- 
lieved to  be  due  to  waste  products  (poisons)  in  the  blood. 

Poisons  produced  by  Alcohol.  —  When  too  little  oxygen  enters  the 
draft  of  the  stove,  the  wood  is  burned  imperfectly,  and  there  are 
clouds  of  smoke  and  irritating  gases.  So,  if  oxygen  unites  with  the 
alcohol  and  too  little  reaches  the  cells,  instead  of  carbon  dioxide, 
water,  and  urea  being  formed,  there  are  other  products,  some 
of  which  are  exceedingly  poisonous  and  which  the  kidneys  handle 
with  difficulty.  The  poisons  retained  in  the  circulation  never  fail 
to  produce  their  poisonous  effects,  as  shown  by  headaches,  clouded 
brain,  pain,  and  weakness  of  the  body.  The  word  "  intoxication  " 
means  ''  in  a  state  of  poisoning."  These  poisons  gradually  accumu- 
late as  the  alcohol  takes  oxygen  from  the  cells.  The  worst  effects 
come  last,  when  the  brain  is  too  benumbed  to  judge  fairly  of  their 
harm. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.    American  Book  Company. 
Davison,  Human  Body  and  Health.     American  Book  Company. 
Gulick,  Hygiene  Series,  Emergencies,  Good  Health.     Ginn  and  Company. 
Hough  and  Sedgwick,  The  Human  Mechanism.     Ginn  and  Company. 
Macy,  General  Physiology.     American  Book  Company. 
Ritchie,  Human  Physiology.    World  Book  Company. 


XXIII.    BODY  CONTROL  AND  HABIT  FORMATION 

Problems.  —  How  is  body  control  jnaintained  f 

(a)  What  is  the  inechanisiiv  of  direction  and  control  ? 

(b)  What  is  the  method  of  direction  and  control? 

(c)  What  are  habits  ?   How  are  they  formed  and  how  brohen  ? 

(d)  Wh(t,t  are  the  organs  of  sense?     What  are  their  uses? 
ie)    How  does  alcohol  affect  the  nervous  system? 

Laboratory  Suggestions 

Demonstration.  —  Sensory  motor  reactions. 

Demonstration.  —  Nervous  system.     Models  and  frog  dissections. 

Demonstration.  —  Neurones  under  compound  microscope  (optional). 

Demonstration.  —  Reflex  acts  are  unconscious  acts  :  show  how  conscious 
acts  may  become  habitual. 

Home  exercise  in  habit  forming. 

The  senses.  —  Home  exercises.  —  (1)  To  determine  areas  most  sensitive 
to  touch.  (2)  To  determine  or  map  out  hot  and  cold  spots  on  an  area  on 
the  wrist.     (3)  To  determine  functions  of  different  areas  on  tongue. 

Demonstration.  —  Show  how  eye  defects  are  tested. 

Laboratory  summary.  —  The  effects  of  alcohol  on  the  nervous  system. 

The  Body  a  Self-directed  Machine.  —  Throughout  the  preced- 
ing chapters  the  body  has  been  likened  to  an  engine,  which,  while 
burning  its  fuel,  food,  has  done  work.  If  we  were  to  carry  our 
comparison  further,  however,  the  simile  ceases.  For  the  engineer 
runs  the  engine,  while  the  bodily  machine  is  self-directive. 

Moreover,  most  of  the  acts  we  perform  during  a  day's  work  are 
results  of  the  automatic  working  of  this  bodily  machine.  The 
heart  pumps ;  the  blood  circulates  its  load  of  food,  oxygen,  and 
wastes ;  the  movements  of  breathing  are  performed  ;  the  thousand 
and  one  complicated  acts  that  go  on  every  day  within  the  body  are 
seemingly  undirected. 

Automatic  Activity.  —  In  addition  to  this,  numbers  of  other  of 
our  daily  acts  are  not  thought  about.     If  we  are  well-regulated 

348 


BODY  CONTROL  AND   HABIT  FORMATION      349 


body  machines,  we 
get  up  in  the  morn- 
ing, automatically 
wash,  clean  our 
teeth,  dress,  go  to 
the  toilet,  get  our 
breakfast,  walk  to 
school,  even  per- 
form such  compli- 
cated processes  as 
that  of  writing, 
without  thinking 
about  or  directing 
the  machine.  In 
these  respects  we 
have  become  crea- 
tures of  habit. 
Certain  acts  which 
once  we  might 
have  learned  con- 
sciously, have  be- 
come automatic. 

But  once  at 
school,  if  we  are 
really  making  good 
in  our  work  in  the 
classroom,  we  be- 
gin a  higher  con- 
trol of  our  bodily 
functions.  Auto- 
matic control  acts 
no  longer,  and  sen- 
sation is  not  the 
only  guide  —  for  we  now  begin  to  make  conscious  choice;  we  weigh 
this  matter  against  another,  —  in  short,  we  think. 

Parts  of  the  Nervous  System.  —  This  wonderful  self-directive 
apparatus  placed  within  us,  which  is  in  part  under  control  of  our 


The  central  nervous  system 


350      BODY   CONTROL  AND   HABIT  FORMATION 

will,  is  known  as  the  nervous  system.  In  the  vertebrate  animals, 
including  man,  it  consists  of  two  divisions.  One  includes  the 
brain,  spinal  cord,  the  cranial  and  spinal  nerves,  which  together 
make  up  the  cerebrospinal  nervous  system.  The  other  division  is 
called  the  sympathetic  nervous  system  and  has  to  do  with  those 
bodily  functions  which  are  beyond  our  control.  Every  group  of 
cells  in  the  body  that  has  work  to  do  (excepting  the  floating  cells 
of  the  blood)  is  directly  influenced  by  these  nerves.  Oar  bodily 
comfort  is  dependent  upon  their  directive  work.  The  organs 
which  put  us  in  touch  with  our  surroundings  are  naturally  at  the 
surface  of  the  body.  Small  collections  of  nerve  cells,  called  ganglia, 
are  found  in  all  parts  of  the  body.  These  nerve  centers  are  con- 
nected, to  a  greater  or  less  degree,  with  the  surface  of  the  body  by 
the  nerves,  which  serve  as  pathwa^^s  between  the  end  organs  of 
touch,  sight,  taste,  etc.,  and  the  centers  in  the  brain  or  spinal  cord. 
Thus  sensation  is  obtained. 

Sensations  and  Reactions.  —  We  have  already  seen  that  simpler 
forms  of  life  perform  certain  acts  because  certain  outside  forces  act- 
ing upon  them  cause  them  to  react  to  the  stimulus  from  without. 
The  one-celled  animal  responds  to  the  presence  of  food,  to  heat,  to 
oxygen,  to  other  conditions  in  its  surroundings.  An  earthworm  is 
repelled  by  light,  is  attracted  by  food.  All  animals,  including  man, 
are  put  in  touch  with  their  surroundings  by  what  we  call  the  or- 
gans of  sensation.  The  senses  of  man,  besides  those  we  commonly 
know  as  those  of  sight,  hearing,  taste,  smell,  and  touch,  are  those  of 
temperature,  pressure,  and  pain.  It  is  obvious  that  such  organs, 
if  they  are  to  be  of  use  to  an  animal,  must  be  at  the  outside  of  the 
body.  Thus  we  find  eyes  and. ears  in  the  head,  and  taste  cells 
in  the  mouth,  while  other  cells  in  the  nose  perceive  odors,  and 
still  others  in  the  skin  are  sensitive  to  heat  or  cold,  pressure  or 
pain. 

But  this  is  not  all.  Strangely  enough,  we  do  not  see  with  our 
eyes  or  taste  with  our  taste  cells.  These  organs  receive  the  sensa- 
tions, and  by  means  of  a  complicated  system  of  greatly  elongated 
cell  structures,  the  message  is  sent  inward,  relayed  by  other  elon- 
gated cells  until  the  sensory  message  reaches  an  inner  station,  in 
the  central  nervous  system.     We  see  and  hear  and  smell  in  our 


BODY   CONTROL  AND   HABIT  FORMATION      351 


"-.Dendrites 


Axon 


brain.     Let  us  next  examine  the  structure  of  the  nerve  cells  or 
neurons  part  of  which  serve  as  pathways  for  these  messages. 

Neurones.  —  A  nerve  cell,  like  other  cells  in  the  body,  is  a  mass 
of  protoplasm  containing  a  nucleus.  But  the  body  of  the  nerve 
cell  is  usually  rather  irregular  in  shape,  and  distinguished  from 
most  other  cells  by  possessing  several  delicate,  branched  proto- 
plasmic projections  called  dendrites.  One  of 
these  processes,  the  axon,  is  much  longer 
than  the  others  and  ends  in  a  muscle  or 
organ  of  sensation.  The  axon  forms  the 
pathway  over  which  nervous  impulses  travel 
to  and  from  the  nerve  centers, 

A  nerve  consists  of  a  bundle  of  such  tiny 
axons,  bound  together  by  connective  tissue. 
As  a  nerve  ganglia  is  a  center  of  activity  in 
the  nervous  system,  so  a  cell  body  is  a  center 
of  activity  which  may  send  an  impulse  over 
this  thin  strand  of  protoplasm  (the  axon) 
prolonged  many  hundreds  of  thousands  of 
times  the  length  of  the  cell.  Some  neurones 
in  the  human  body,  although  visible  only 
under  the  compound  microscope,  give  rise 
to  axons  several  feet  in  length. 

Because  some  bundles  of  axons  originate 
in  organs  that  receive  sensations  and  send 
those  sensations  to  the  central  nervous  sys- 
tem, they  are  called '  sensory  nerves.  Other 
axons  originate  in  the  central  nervous  system  and  pass  outward 
as  nerves  producing  movement  of  muscles.  These  are  called 
motor  nerves. 

The  Brain  of  Man.  —  In  man,  the  central  nervous  system  consists  of  a 
brain  and  spinal  cord  inclosed  in  a  bony  case.  From  the  brain,  twelve 
pairs  of  nerves  are  given  off ;  thirty-one  pairs  more  leave  the  spinal  cord. 
The  brain  has  three  divisions.  The  cerebrum  makes  up  the  largest  part.' 
In  this  respect  it  differs  from  the  cerebrum  of  the  frog  and  other  verte- 
brates. It  is  divided  into  two  lobes,  the  hemispheres,  which  are  connected 
with  each  other  by  a  broad  band  of  nerve  fibers.    The  outer  surface  of  the 


Nerve-enda 


Diagram  of  a  neuron  or 
nerve  unit. 


352      BODY   CONTROL   AND   HABIT  FORMATION 

cerebrum  is  thrown  into  folds  or  convolutions  which  give  a  large  surface, 
the  cell  bodies  of  the  neurons  being  found  in  this  part  of  the  cerebrum. 
Holding  the  cell  bodies  and  fibers  in  place  is  a  kind  of  connective  tissue. 
The  inner  part  (white  in  color)  is  composed  largely  of  fibers  which  pass 
to  other  parts  of  the  brain  and  down  into  the  spinal  cord.  Under  the 
cerebrum,  and  dorsal  to  it,  hes  the  httle  brain,  or  cerebellum.  The  two 
sides  of  the  cerebellum  are  connected  by  a  band  of  nerve  fibers  which 
run  around  into  the  lower  hindbrain  or  medulla.  This  band  of  fibers  is 
called  the  pons.  The  medulla  is,  in  structure,  part  of  the  spinal  cord,  and 
is  made  up  largely  of  fibers  running  longitudinally. 

The  Sympathetic  Nervous  System.  —  Connected  with  the  central  ner- 
vous system  is  that  part  of  the  nervous  apparatus  that  controls  the  mus- 
cles of  the  digestive  tract  and  blood  vessels,  the  secretions  of  gland  cells, 
and  all  functions  which  have  to  do  with  life  processes  in  the  body.  This 
is  called  the  sympathetic  nervous  system. 

Functions  of  the  Parts  of  the  Central  Nervous  System  of  the 
Frog.  —  From  careful  study  of  living  frogs,  birds,  and  some  mam- 
mals we  have  learned  much  of  what  we  know  of  the  functions  of 
the  parts  of  the  central  nervous  system  in  man. 

It  has  been  found  that  if  the  entire  brain  of  a  frog  is  destroyed 
and  separated  from  the  spinal  cord,  ''  the  frog  will  continue  to 
live,  but  with  a  very  peculiarly  modified  activity."  It  does  not 
appear  to  breathe,  nor  does  it  swallow.  It  will  not  move  or  croak, 
but  if  acid  is  placed  upon  the  skin  so  as  to  irritate  it,  the  legs  make 
movements  to  push  away  and  to  clean  off  the  irritating  substance. 
The  spinal  cord  is  thus  shown  to  be  a  center  for  defensive  move- 
ments. If  the  cerebrum  is  separated  from  the  rest  of  the  nervous 
system,  the  frog  seems  to  act  a  little  differently  from  the  normal 
animal.  It  jumps  when  touched,  and  swims  when  placed  in  water. 
It  will  croak  when  stroked,  or  swallow  if  food  be  placed  in  its  mouth. 
But  it  manifests  no  hunger  or  fear,  and  is  in  every  sense  a  machine 
which  will  perform  certain  actions  after  certain  stimulations.  Its 
movements  are  automatic.  If  now  we  watch  the  movements  of 
a  frog  which  has  the  brain  uninjured  in  any  way,  we  find  that  it 
acts  spontaneously.  It  tries  to  escape  when  caught.  It  feels 
hungry  and  seeks  food.  It  is  capable  of  voluntary  action.  It 
acts  like  a  normal  individual. 


1 


BODY  CONTROL  AND   HABIT   FORMATION      353 

Functions  of  the  Cerebrum.  —  In  general,  the  functions  of  the 
different  parts  of  the  brain  in  man  agree  with  those  functions 
we  have  already  observed  in  the  frog.  The  cerebrum  has  to  do 
with  conscious  activity ;  that  is,  thought.  It  presides  over  what 
we  call  our  thoughts,  our  will,  and  our  sensations.  A  large  part 
of  the  area  of  the  outer  layer  of  the  cerebrum  seems  to  be  given 
over  to  some  one  of  the  different  functions  of  speech,  hearing, 
sight,  touch,  movements  of  bodily  parts.      The  movement  of  the 


^t^Qioisr 


Cerebrum 


Cerebellum 

Medulla 

Spinal  Cord 


Diagram  to  show  the  parts  of  the  brain  and  action  of  the  different  parts  of  the 

brain. 

smallest  part  of  the  body  appears  to  have  its  definite  localized 
center  in  the  cerebrum.  Experiments  have  been  performed  on  mon- 
keys, and  these,  together  with  observations  made  on  persons  who 
had  lost  the  power  of  movement  of  certain  parts  of  the  body, 
and  who,  after  death,  were  found  to  have  had  diseases  localized 
in  certain  parts  of  the  cerebrum,  have  given  to  us  our  knowledge 
on  this  subject. 

Reflex  Actions ;    their   Meaning.  —  If  through  disease  or  for 
other  reasons  the  cerebrum  does  not  function,  no  will  power  is 

HUNTER,    CIV.    BI. 23 


354      BODY   CONTROL  AND   HABIT  FORMATION 


Diagram  of  the  nerve  path  of  a  simple  reflex  action. 


exerted,  nor  are  intelligent  acts  performed.  All  acts  performed  in 
such  a  state  are  known  as  reflex  actions.  The  involuntary  brush- 
ing of  a  fly  from  the  face,  or  the  attempt  to  move  away  from  the 

source  of  annoyance 
when  tickled  with  a 
feather,  are  examples 
of  reflexes.  In  a 
reflex  act,  a  person 
does  not  think  before 
acting.  The  nervous 
impulse  comes  from 
the  outside  to  cells 
that  are  not  in  the 
cerebrum.  The  mes- 
sage is  short-circuited 
back  to  the  surface 
by  motor  nerves,  without  ever  having  reached  the  thinking 
centers.  The  nerve  cells  which  take  charge  of  such  acts  are  lo- 
cated in  the  cerebellum  or  spinal  cord. 

Automatic  Acts.  —  Some  acts,  however,  are  learned  by  con- 
scious thought,  as  writing,  walking,  running,  or  swimming.  Later 
in  life,  however,  these  activities  become  automatic.  The  actual 
performance  of  the  action  is  then  taken  up  by  the  cerebellum, 
medulla,  and  spinal  ganglia.  Thus  the  thinking  portion  of  the 
brain  is  relieved  of  part  of  its  work. 

Bundles  of  Habits.  —  It  is  surprising  how  little  real  thinking  we 
do  during  a  day,  for  most  of  our  acts  are  habitual.  Habit  takes 
care  of  our  dressing,  our  bathing,  our  care  of  the  body  organs,  our 
methods  of  eating ;  even  our  movements  in  walking  and  the  kind 
of  hand  we  write  are  matters  of  habit  forming.  We  are  bundles  of 
habits,  be  they  good  ones  or  bad  ones. 

Habit  Formation.  —  The  training  of  the  different  areas  in  the 
cerebrum  to  do  their  work  well  is  the  object  of  education.  When 
we  learned  to  write,  we  exerted  conscious  effort  in  order  to  make 
the  letters.  Now  the  act  of  forming  the  letters  is  done  without 
thought.  By  training,  the  act  has  become  automatic.  In  the 
beginning,  a  process  may  take  much  thought  and  many  trials 


BODY   CONTROL  AND   HABIT  FORMATION      355 

before  we  are  able  to  complete  it.  After  a  little  practice,  the  same 
process  may  become  almost  automatic.  We  have  formed  a  habit. 
Habits  are  really  acquired  reflex  actions.  They  are  the  result  of 
nature's  method  of  training.  The  conscious  part  of  the  brain  has 
trained  the  cerebellum  or  spinal  cord  to  do  certain  things  that,  at 
first,  were  taken  charge  of  by  the  cerebrum. 

Importance  of  Forming  Right  Habits.  —  Among  the  habits  early 
to  be  acquired  are  the  habits  of  studying  properly,  of  concentrating 
the  mind,  of  learning  self-control,  and,  above  all,  of  contentment. 
Get  the  most  out  of  the  world  about  you.  Remember  that  the 
immediate  effect  in  the  study  of  sdme  subjects  in  school  may  not 
be  great,  but  the  cultivation  of  correct  methods  of  thinking  may  be 
of  the  greatest  importance  later  in  life.  The  man  or  woman  who 
has  learned  how  to  concentrate  on  a  problem,  how  to  weigh  all  sides 
with  an  unbiased  mind,  and  then  to  decide  on  what  they  believe  to 
be  best  and  right  are  the  efficient  and  happy  ones  of  their  generation. 

"  The  hell  to  be  endured  hereafter,  of  which  theology  tells,  is  no  worse 
than  the  hell  we  make  for  ourselves  in  this  world  by  habitually  fashioning 
our  characters  in  the  wrong  way.  Could  the  young  but  realize  how  soon 
they  will  become  mere  walking  bundles  of  habits,  they  would  give  more 
heed  to  their  conduct  while  in  the  plastic  state.  We  are  spinning  our 
own  fates,  good  or  evil,  and  never  to  be  undone.  Every  smallest  stroke 
of  virtue  or  of  vice  leaves  its  never-so-little  scar.  The  drunken  Rip  Van 
Winkle,  in  Jefferson's  play,  excuses  himself  for  every  fresh  dereUction  by 
saying,  '  I  won't  count  this  time !  '  Well !  he  may  not  count  it,  and  a 
kind  Heaven  may  not  count  it;  but  it  is  being  counted  none  the  less. 
Down  among  his  nerve  cells  and  fibers  the  molecules  are  counting  it,  regis- 
tering and  storing  it  up  to  be  used  against  him  when  the  next  temptation 
comes.  Nothing  we  ever  do  is,  in  strict  scientific  literalness,  wiped  out. 
Of  course  this  has  its  good  side  as  well  as  its  bad  one.  As  we  become  per- 
manent drunkards  by  so  many  separate  drinks,  so  we  become  saints  in  the 
moral,  and  authorities  in  the  practical  and  scientific,  spheres  by  so  many 
separate  acts  and  hours  of  work.  Let  no  youth  have  any  anxiety  about 
the  upshot  of  his  education,  whatever  the  line  of  it  may  be.  If  he  keep 
faithfully  busy  each  hour  of  the  working  day,  he  may  safely  leave  the  final 
result  to  itself.  He  can  with  perfect  certainty  count  on  waking  up  some 
fine  morning,  to  find  himself  one  of  the  competent  ones  of  his  generation, 
in  whatever  pursuit  he  may  have  singled  out."  —  James,  Psychology. 


356      BODY   CONTROL  AND   HABIT  FORMATION 


Some  Rules  for  Forming  Good  Habits.  —  Professor  Home  gives 
several  rules  for  making  good  or  breaking  bad  habits.  They  are  : 
'' First,  ad  on  every  opportunity.  Second,  make  a  strong  start. 
Third,  allow  no  exception.  Fourth,  for  the  had  habit  establish  a  good 
one.  Fifth,  summoning  all  the  man  within,  use  effort  of  will.'" 
Why  not  try  these  out  in  forming  some  good  habit?  You  will 
find  them  effective. 

Necessity  of  Food,  Fresh  Air,  and  Rest.  —  The  nerve  cells,  like 
all  other  cells  in  the  body,  are  continually  wasting  away  and  being 
rebuilt.  Oxidation  of  food  material  is  more  rapid  when  we  do 
mental  work.  The  cells  of  the  brain,  like  muscle  cells,  are  not 
only  capable  of  fatigue,  but  show  this  in  changes  of  form  and  of 

contents.  Food  brought  to  them  in  the 
blood,  plenty  oi  fresh  air,  especially  when 
engaged  in  active  brain  work,  and  rest 
at  proper  times,  are  essential  in  keeping 
the  nervous  system  in  condition.  One 
of  the  best  methods  of  resting  the  brain 
cells  is  a  change  of  occupation.  Tennis, 
golf,  baseball,  and  other  outdoor  sports 
combine    muscular    exercise    with    brain 


a 


The  effect  of  fatigue  on  nerve  activity  of  a  different  sort  from  that  of 

cells.       a,     healthy     brain    r       •  v,      i  i 

6,  fatigued  brain  cell,    busmess    or    School    WOrk. 


cell 


But  change 
of  occupation  will  not  rest  exhausted 
neurones.  For  this,  sleep  is  necessary.  Especially  is  sleep  an 
important  factor  in  the  health  of  the  nervous  system  of  growing 
children. 

Necessity  of  Sleep.  —  Most  brain  cells  attain  their  growth 
early  in  life.  Changes  occur,  however,  until  some  time  after  the 
school  age.  Ten  hours  of  sleep  should  be  allowed  for  a  child,  and 
at  least  eight  hours  for  an  adult.  At  this  time,  only,  do  the  brain 
cells  have  opportunity  to  rest  and  store  food  and  energy  for  their 
working  period. 

Sleep  is  one  way  in  which  all  cells  in  the  body,  and  particularly 
those  of  the  nervous  system,  get  their  rest.  The  nervous  system, 
by  far  the  most  delicate  and  hardest-worked  set  of  tissues  in  the 
body,  needs  rest  more  than  do  other  tissues,  for  its  work  directing 


BODY   CONTROL   AND   HABIT   FORMATION      357 

the  body  only  ends  with  sleep  or  unconsciousness.  The  afternoon 
nap,  snatched  by  the  brain  worker,  gives  him  renewed  energy  for 
his  evening's  work.  It  is  not  hard  application  to  a  task  that 
wearies  the  brain ;  it  is  continuous  work  without  rest. 


THE   SENSES 

Touch.  —  In  animals  having  a  hard  outside  covering,  such  as  certain 
worms,  insects,  and  crustaceans,  minute  hairs,  which  are  sensitive  to  touch, 
are  found  growing  oiit  from  the  body  covering.  At  the  base  of  these  hairs 
are  found  neurones  which  send  axons  inward  to  the  central  nervous  sj^stem. 
Organs  of  Touch.  —  In  man,  the  nervous  mechanism  which  governs 
touch  is  located  in  the  folds  of  the  dermis  or  in  the  skin.  Special  nerve 
endings,  called  the  tactile  corpus- 
cles, are  found  there,  each  in-  _6 
closed  in  a  sheath  or  capsule  of 
connective  tissue.  Inside  is  a 
complicated  nerve  ending,  and 
axons  pass  inward  to  the  central 
nervous  system.  The  number 
of  tactile  corpuscles  present  in  a 
given  area  of  the  skin  determines 
the  accuracy  and  ease  with  which 
objects  may  be  known  by  touch. 

If  you  test  the  different  parts 
of  the  body,  as  the  back  of  the 
hand,  the  neck,  the  skin  of  the 
arm,  of  the  back,  or  the  tip  of 
the  tongue,  with  a  pair  of  open 

dividers,  a  vast  difference  in  the  accuracy  with  which  the  two  points 
may  be  distinguished  is  noticed.  On  the  tip  of  the  tongue,  the  two  points 
need  only  be  separated  by  2V  of  ^^  iiich  to  be  so  distinguished.  In  the 
small  of  the  back,  a  distance  of  2  inches  may  be  reached  before  the  dividers 
feel  like  two  points. 

Temperature,  Pressure,  Pain.  —  The  feeling  of  temperature,  pressure, 
and  pain  is  determined  by  different  end  organs  in  the  skin.  Two  kinds 
of  nerve  fibers  exist  in  the  skin,  which  give  distinct  sensations  of  heat  and 
cold.  These  nerve  endings  can  be  located  by  careful  experimentation. 
There  are  also  areas  of  nerve  endings  which  are  sensitive  to  pressure, 
and  still  others,  most  numerous  of  all,  sensitive  to  pain. 


Nerves  in  the  skin:  a,  nerve  fiber;  6,  tactile 
papillae,  containing  a  tactile  corpuscle ; 
c,  papillae  containing  blood  vessels. 
(After  Benda.) 


358      BODY   CONTROL  AND   HABIT  FORMATION 


Taste  Cells 

^Supporting 
'      Cells 


c 

A,  isolated  taste  bud, 
from  whose  upper  free 
end  project  the  ends  of 
the  taste  cells ;  B,  sup- 
porting or  protecting 
cell ;    C,  sensory  cell. 


Taste  Organs.  —  The  surface  of  the  tongue  is  folded  into  a  number  of 
Httle  projections  known  as  papillae.  These  may  be  more  easily  found  on 
your  own  tongue  if  a  drop  of  vinegar  is  placed  on  its  broad  surface.     In  the 

folds,  between  these  projections  on  the  top  and 
back  part  of  the  tongue,  are  located  the  organs  of 
taste.     These  organs  are  called  taste  buds. 

Each  taste  bud  consists  of  a  collection  of 
spindle-shaped  neurones,  each  cell  tipped  at  its 
outer  end  with  a  hairlike  projection.  These  cells 
send  inward  fibers  to  other  cells,  the  fibers  from 
which  ultimately  reach  the  brain.  The  sensory 
cells  are  surrounded  by  a  number  of  projecting 
cells  which  are  arranged  in  layers  about  them. 
Thus  the  organ  in  longitudinal  section  looks 
somewhat  like  an  onion  cut  lengthwise. 

How  we  Taste.  —  Four  kinds  of  substances 
may  be  distinguished  by  the  sense  of  taste.  These 
are  sweet,  sour,  bitter,  and  salt.  Certain  taste  cells  located  near  the 
back  of  the  tongue  are  stimulated  only  by  a  bitter  taste.  Sweet  sub- 
stances are  perceived  by  cells  near  the  tip  of  the  tongue,  sour  substances 
along  the  sides,  and  salt  about  equally  all  over  the  surface.  A  substance 
must  be  dissolved  in  fluid  in  order  to  be  tasted.  Many  things  which 
we  beheve  we  taste  are  in  reality  perceived  by  the  sense  of  smell.  Such 
are  spicy  sauces  and  flavors  of  meats  and  vegetables.  This  may  easily 
be  proved  by  holding  the  nose  and  chewing,  with  closed  eyes,  several 
different  substances,  such  as  an  apple,  an  onion,  and  a  raw  potato. 

Smell.  —  The  sense  of  smell  is  located  in  the  membrane  hning  the  upper 
part  of  the  nose.  Here  are  found  a  large  number  of  rod-shaped  cells  wliich 
are  connected  with  the  brain  by  means  of  the  olfactory  nerve.  In  order 
to  perceive  odors,  it  is  necessary  to  have  them  diffused  in  the  air ;  hence 
we  sniff  so  as  to  draw  in  more  air  over  the  olfactory  ceUs. 

The  Organ  of  Hearing.  —  The  organ  of  hearing  is  the  ear.  The  outer 
ear  consists  of  a  funnel-like  organ  composed  largely  of  cartilage  which  is 
of  use  in  collecting  sound  waves.  This  part  of  the  ear  incloses  the  audi- 
tory canal,  which  is  closed  at  the  irmer  end  by  a  tightly  stretched  mem- 
brane, the  tympajiic  membrane  or  ear  drum.  The  function  of  the  tym- 
panic membrane  is  to  receive  sound  waves,  for  all  sound  is  caused  by 
vibrations  in  the  air,  these  vibrations  being  transmitted,  by  the  means 
of  a  comphcated  apparatus  found  in  the  middle  ear,  to  the  real  organ  of 
hearing  located  in  the  inner  ear. 


BODY   CONTROL  AND   HABIT   FORMATION      359 


J^ail. 


JEJ.M. 


Middle  Ear.  —  The  middle  ear  in  man  is  a  cavity  inclosed  by  the  tem- 
poral bone,  and  separated*  from  the  outer  ear  by  the  tympanic  membrane. 
A  little  tube  called  the  Eustachian  tube  connects  the  inner  ear  with  the 
mouth  cavity.  By  allowing  air  to  enter  from  the  mouth,  the  air  pressure 
is  equalized  on  the  ear  drum.  For  this  reason,  we  open  the  mouth  at  the 
time  of  a  heavy  concussion  and  thus  prevent  the  rupture  of  the  delicate 
tympanic  membrane. 
Placed  directly  against 
the  tympanic  mem- 
brane and  connecting 
it  with  the  inner  ear  is 
a  chain  of  three  tiny 
bones,  the  smallest 
bones  of  the  body.  The 
outermost  is  called  the 
hammer;  the  next  the 
anvil;  the  third  the 
stirrup .  All  three  bones 
are  so  called  from  their 
resemblances  in  shape 
to  the  articles  for  which 
they  are  named.  These 
bones  are  held  in  place 
by  very  small  muscles 
which  are  delicately 
adjusted  so  as  to  tighten  or  relax  the  membranes  guarding  the  middle  and 
inner  ear. 

The  Inner  Ear.  —  The  inner  ear  is  one  of  the  most  complicated,  as 
well  as  one  of  the  most  delicate,  organs  of  the  body.  Deep  within  the 
temporal  bone  there  are  found  two  parts,  one  of  which  is  called,  collec- 
tively, the  semicircular  canal  region,  the  other  the  cochlea,  or  organ  of  hear- 
ing. 

It  has  been  discovered  by  experimenting  with  fish,  in  which  the  semi- 
circular canal  region  forms  the  chief  part  of  the  ear,  that  this  region  has 
to  do  with  the  equilibrium  or  balancing  of  the  body.  We  gain  in  part  our 
knowledge  of  our  position  and  movements  in  space  by  means  of  the  semi- 
circular canals. 

That  part  of  the  ear  which  receives  sound  waves  is  known  as  the  cochlea, 
or  snail  shell,  because  of  its  shape.  This  very  compHcated  organ  is  lined 
with  sensory  cells  provided  with  ciUa.     The  cavity  of  the  cochlea  is  filled 


Section  of  ear  :  E.M.,  auditory  canal ;  Ty.M.,  tympanic 
membrane  ;  Eu.,  Eustachian  tube  ;  Ty,  middle  ear  ; 
Coc,  A.S.C.,  E.S.C.,  etc.,  internal  ear. 


360      BODY   CONTROL  AND   HABIT   FORMATION 


with  a  fluid.  It  is  believed  that  somewhat  as  a  stone  thrown  into  water 
causes  ripples  to  emanate  from  the  spot  where  it  strikes,  so  sound  waves 
are  transmitted  by  means  of  the  fluid  filUng  the  cavity  to  the  sensory  cells 
of  the  cochlea  (collectively  known  as  the  organ  of  Corti)  and  thence  to  the 
brain  by  means  of  the  auditory  nerve. 

The  Character  of  Sound.  —  When  vibrations  which  are  received  by  the 
ear  follow  each  other  at  regular  intervals,  the  sound  is  said  to  be  musical. 
If  the  vibrations  come  irregularly,  we  call  the  sound  a  noise.  If  the  vibra- 
tions come  slowly,  the  pitch  of  the  sound  is  low ;  if  they  come  rapidly,  the 
pitch  is  high.  The  ear  is  able  to  perceive  as  low  as  thirty  vibrations  per 
second  and  as  high  as  almost  thirty  thousand.  The  ear  can  be  trained  to 
recognize  sounds  which  are  unnoticed  in  untrained  ears. 

The  Eye.  —  The  eye  or  organ  of  vision  is  an  almost  spherical  body  which 
fits  into  a  socket  of  bone,  the  orbit.     A  stalklike  structure,  the  optic  nerve, 

connects  the  eye  with  the  brain.  Free 
movement  is  obtained  by  means  of  six 
little  muscles  which  are  attached  to 
the  outer  coat,  the  eyeball,  and  to  the 
bony  socket  around  the  eye. 

The  wall  of  the  eyeball  is  made  up 
of  three  coats.  An  outer  tough  white 
coat,  of  connective  tissue,  is  called  the 
sclerotic  coat.  Under  the  sclerotic 
coat,  in  front,  the  eye  bulges  outward 
a  little.  Here  the  outer  coat  is  con- 
tinuous with  a  transparent  tough  layer 
called  the  cornea.  A  second  coat,  the  choroid,  is  supplied  with  blood 
vessels  and  cells  which  bear  pigments.  It  is  a  part  of  this  coat  which 
we  see  through  the  cornea  as  the  colored  part  of  the  eye  (the  iris). 
In  the  center  of  the  iris  is  a  small  circular  hole  (the  pupil).  The  iris 
is  under  the  control  of  muscles,  and  may  be  adjusted  to  varying 
amounts  of  light,  the  hole  becoming  larger  in  dim  light,  and  smaller 
in  bright  light.  The  inmost  layer  of  the  eye  is  called  the  retina.  This 
is,  perhaps,  the  most  delicate  layer  in  the  entire  body.  Despite  the 
fact  that  the  retina  is  less  than  ^  of  an  inch  in  thickness,  there  are 
several  layers  of  cells  in  its  composition.  The  optic  nerve  enters  the 
eye  from  behind  and  spreads  out  to  form  the  surface  of  the  retina. 
Its  finest  fibers  are  ultimately  connected  with  numerous  elongated 
cells  which  are  stimulated  by  light.  The  retina  is  dark  purple  in  color, 
this  color  being  caused  by  a  layer  of  cells  next  to  the  choroid  coat^    This 


■Muscle 


Sclerotic  Coat 


Longitudinal  section  through 
the  eye. 


BODY   CONTROL  AND   HABIT  FORMATION      361 

accounts  for  the  black  appearance  of  the  pupil  of  the  eye,  when  we  look 
through  the  pupil  into  the  darkened  space  within  the  eyeball.  The 
retina  acts  as  the  sensitized  plate  in  the  camera,  for  on  it  are  received  the 
impressions  which  are  transformed  and  sent  to  the  brain  as  sensations  of 
sight.  The  eye,  like  the  camera,  has  a  lens.  This  lens  is  formed  of 
transparent,  elastic  material.  It  is  found  directly  behind  the  iris  and  is 
attached  to  the  choroid  coat  by  means  of  delicate  ligaments.  In  front  of 
the  lens  is  a  small  cavity  filled  with  a  watery  fluid,  the  aqueous  humor, 
while  behind  it  is  the  main  cavity  of  the  eye,  filled  with  a  transparent, 
almost  jelly  like,  vitreous  hujnor.  The  lens  itself  is  elastic.  This  circum- 
stance permits  of  a  change  of  form  and,  in  consequence,  a  change  of 
focus  upon  the  retina  of  the  lens.  By  means  of  this  change  in  form,  or 
accommodation,  we  are  able  to  distinguish  between  near  and  distant 
objects. 

Defects  in  the  Eye.  — •  In  some  eyes,  the  lens  is  in  focus  for  near  objects, 
but  is  not  easily  focused  upon  distant  objects ;  such  an  eye  is  said  to  be 
nearsighted.  Other  ej^es 
which  do  not  focus  clearly 
on  objects  near  at  hand  are 

said  to  be  farsighted.     Still     ^^       ^  ,,,,.« 

.  ,  How   far   away   can   you   read    these    letters: 

another  eye  detect  is  astig-  Measure   the    distance.      Twenty   feet    is    a 

matism,  which  causes  images  test  for  the  normal  eye. 

of  lines  in  a  certain  direction 

to  be  indistinct,  while  images  of  lines  transverse  to  the  former  are  distinct. 
Many  nervous  troubles,  especially  headaches,  may  be  due  to  eye  strain. 
We  should  have  our  eyes  examined  from  time  to  time,  especially  if  we  are 
subject  to  headaches. 

The  Alcohol  Question.  —  It  is  agreed  by  investigators  that  in 
large  or  continued  amounts  alcohol  has  a  narcotic  effect ;  that  it 
first  dulls  or  paralyzes  the  nerve  centers  which  control  our  judg- 
ment, and  later  acts  upon  the  so-called  motor  centers,  those  which 
control  our  muscular  activities. 

The  reason,  then,  that  a  man  in  the  first  stages  of  intoxication 
talks  rapidly  and  sometimes  wittily,  is  because  the  centers  of  judg- 
ment are  paralyzed.  This  frees  the  speech  centers  from  control 
exercised  by  our  judgment,  with  the  resultant  rapid  and  free  flow 
of  speech. 

In  small  amounts  alcohol  is  believed  by  some  physiologists  to 
have  always  this  same  narcotic  effect,  while  other  physiologists 


Y  F  E  V 


362      BODY  CONTROL  AND   HABIT  FORMATION 

think  that  alcohol  does  stimulate  the  brain  centers,  especially 
the  higher  centers,  to  increased  activity.  Some  scientific  and  pro- 
fessional men  use  alcohol  in  small  amounts  for  this  stimulation  and 
report  no  seeming  harm  from  the  indulgence.  Others,  and  by 
far  the  larger  number,  agree  that  this  stimulation  from  alcohol  is 
only  apparent  and  that  even  in  the  smallest  amounts  alcohol  has 
a  narcotic  effect. 

The  Paralyzing  Effects  of  Alcohol  on  the  Nervous  System.  — 
Alcohol  has  the  effect  of  temporarily  paralyzing  the  nerve  centers. 
The  first  effect  is  that  of  exhilaration.  A  man  may  do  more  work 
for  a  time  under  the  stimulation  of  alcohol.  This  stimulation, 
however,  is  of  short  duration  and  is  invariably  followed  by  a  period 
of  depression  and  inertia.  In  this  latter  state,  a  man  will  do  less 
work  than  before.  In  larger  quantities,  alcohol  has  the  effect  of 
completely  paralyzing  the  nerve  centers.  This  is  seen  in  the  case 
of  a  man  "  dead  drunk."  He  falls  in  a  stupor  because  all  of  the 
centers  governing  speech,  sight,  locomotion,  etc.,  have  been  tem- 
porarily paralyzed.  If  a  man  takes  a  very  large  amount  of  al- 
cohol, even  the  nerve  centers  governing  respiration  and  circulation 
may  become  poisoned,  and  the  victim  will  die. 

Effect  on  the  Organs  of  Special  Sense.  —  Professor  Forel,  one  of 
the  foremost  European  experts  on  the  question  of  the  effect  of 
alcohol  on  the  nervous  system,  says :  '^  Through  all  parts  of  ner- 
vous activity  from  the  innervation  of  the  muscles  and  the  simplest 
sensation  to  the  highest  activity  of  the  soul  the  paralyzing  effect 
of  alcohol  can  be  demonstrated."  Several  experimenters  of  un- 
doubted ability  have  noted  the  paralyzing  effect  of  alcohol  even 
in  small  doses.  By  the  use  of  delicate  instruments  of  precision. 
Ridge  tested  the  effect  of  alcohol  on  the  senses  of  smell,  vision,  and 
muscular  sense  of  weight.  He  found  that  two  drams  of  absolute 
alcohol  produced  a  positive  decrease  in  the  sensitiveness  of  the 
nerves  of  feeling,  that  so  small  a  quantity  as  one  half  dram  of 
absolute  alcohol  diminished  the  power  of  vision  and  the  muscular 
sense  of  weight.  Kraepelin  and  Kurz  by  experiment  determined 
that  the  acuteness  of  the  special  senses  of  sight,  hearing,  touch, 
taste,  and  smell  was  diminished  by  an  ounce  of  alcohol,  the  power 
of  vision  being  lost  to  one  third  of  its  extent  and  a  similar  effect 


BODY    COJNTUOL  AND   HABIT   FORMATION      363 


being  produced  on  the  other  special  senses.  Other  investigators 
have  reached  like  conclusions.  There  is  no  doubt  but  that  alcohol, 
even  in  small  quantities,  renders  the  organs  of  sense  less  sensitive 
and  therefore  less  accurate. 

Effect  of  Alcohol  on  the  Ability  to  Resist  Disease.  —  Among 
certain  classes  of  people  the  belief  exists  that  alcohol  in  the  form 
of  brandy  or  some  other  drink  or  in  patent  medicines,  malt  tonics, 


Table  to  show  a  comparison  of  chances  of  illness  and  death  in  drinkers  and 
non-drinkers.     Solid  black,  drinkers.     (From  German  sources.) 

and  the  like  is  of  great  importance  in  building  up  the  body  so  as 
to  resist  disease  or  to  cure  it  after  disease  has  attacked  it.  Nothing 
is  further  from  the  truth.  In  experiments  on  a  large  number  of 
animals,  including  dogs,  rabbits,  guinea  pigs,  fowls,  and  pigeons, 
Laitenen,  of  the  University  of  Helsingsfors,  found  that  alcohol,  with- 
out exception,  made  these  animals  more  susceptible  to  disease  than 
were  the  controls. 

One  of  the  most  serious  effects  of  alcohol  is  the  lowered 
resistance  of  the  body  to  disease.  It  has  been  proved  that  a 
much  larger  proportion  of  hard  drinkers  die  from  infectious  or 
contagious  diseases  than  from  special  diseased  conditions  due 
to  the  direct  action  of  alcohol  on  the  organs  of  the  body.     This 


364      BODY  CONTROL  AND  HABIT  FORMATION 

lowered  resistance  is  shown  in  increased  liability  to  contract 
disease  and  increased  severity  of  the  disease.  We  have  already 
alluded  to  the  findings  of  insurance  companies  with  reference  to 
the  length  of  life  —  the  abstainers  from  alcohol  have  a  much 
better  chance  of  a  longer  life  and  much  less  likelihood  of  infection 
by  disease  germs. 

Use  of  Alcohol  in  the  Treatment  of  Disease.  —  In  the  London 
Temperance  Hospital  alcohol  was  prescribed  seventy-five  times 
in  thirty-three  years.  The  death  rate  in  this  hospital  has 
been  lower  than  that  of  most  general  hospitals.  Sir  William 
Collins,  after  serving  nineteen  years  as  surgeon  in  this  hospital, 
said :  — 

"  In  my  experience,  speaking  as  a  surgeon,  the  use  of  alcohol  is 
not  essential  for  successful  surgery.  ...  At  the  .  London  Tem- 
perance Hospital,  where  alcohol  is  very  rarely  prescribed,  the  mor- 
tality in  amputation  cases  and  in  operation  cases  generally  is  re- 
markably low.  Total  abstainers  are  better  subjects  for  operation, 
and  recover  more  rapidly  from  accidents,  than  those  who  habitu- 
ally take  stimulants." 

In  a  paper  read  at  the  International  Congress  on  Tuberculosis,  in 
New  York,  1906,  Dr.  Crothers  remarked  that  alcohol  as  a  remedy 
or  a  preventive  medicine  in  the  treatment  of  tuberculosis  is  a  most 
dangerous  drug,  and  that  all  preparations  of  sirups  containing 
spirits  increase,  rather  than  diminish,  the  disease. 

Dr.  Kellogg  says :  "  The  paralyzing  influence  of  alcohol  upon 
the  white  cells  of  the  blood  —  a  fact  which  is  attested  by  all 
investigators  — ■  is  alone  sufficient  to  condemn  the  use  of  this  drug 
in  acute  or  chronic  infections  of  any  sort." 

The  Effect  of  Alcohol  upon  Intellectual  Ability.  —  With  regard 
to  the  supposed  quickening  of  the  mental  processes  Horsley  and 
Sturge,  in  their  recent  book,  Alcohol  and  the  Human  Body,  say : 
"  Kraepelin  found  that  the  simple  reaction  period,  by  which  is 
meant  the  time  occupied  in  making  a  mere  response  to  a  signal,  as, 
for  instanc'e,  to  the  sudden  appearance  of  a  flag,  was,  after  the  in- 
gestion of  a  small  quantity  of  alcohol  (J  to  |  ounce),  slightly  accel- 
erated ;  that  there  was,  in  fact,  a  slight  shortening  of  the  time,  as 
though  the  brain  were  enabled  to  operate  more  quickly  than  be- 


BODY   CONTROL  AND  HABIT  FORMATION      365 


fore.  But  he  found  that  after  a  few  minutes,  in  most  cases,  a 
slowing  of  mental  action  began,  becoming  more  and  more  marked, 
and  enduring  as  long  as  the  alcohol  was  in  active  operation  in  the 
body,  i.e.  four  to  five  hours.  .  .  .  Kraepelin  found  that  it  was 
only  more  or  less  automatic  work,  such  as  reading  aloud,  which  was 
quickened  by  alcohol,  though  even  this  was  rendered  less  trust- 
worthy and  accurate."  Again :  "  Kraepelin  had  always  shared 
the  popular  belief  that  a  small  quantity  of  alcohol  (one  to  two 
teaspoonfuls)  had  an  accelerating  effect  on  the  activity  of  his  mind, 


Average  yvuyY{\)e'r  ji^ures 


Conditions, 


3ix 

TiorvalcolaoL 
days. 


1280.66 


Twelve 
alcokol 
days. 


I06J.3 


non-aLcokol 

Two 

alcoViol 
days. 


1086 


Effect  of  use  of  alcohol  on  memory. 

enabling  him  to  perform  test  operations,  as  the  adding  and  sub- 
tracting and  learning  of  figures  more  quickly.  But  when  he  came 
to  measure  with  his  instruments  the  exact  period  and  time  occupied, 
he  found,  to  his  astonishment,  that  he  had  accomplished  these 
mental  operations,  not  more,  but  less,  quickly  than  before.  .  .  . 
Numerous  further  experiments  were  carried  out  in  order  to  test 
this  matter,  and  these  proved  that  alcohol  lengthens  the  time  taken 
to  perform  com.plex  mental  processes,  while  by  a  singular  illusion  the 
person  experimented  upon  imagines  that  his  psychical  actions  are 
rendered  more  rapid." 


366      BODY  CONTROL  AND   HABIT   FORMATION 


Attention  —  that  is,  the  power  of  the  mind  to  grasp  and  con- 
sider impressions  obtained  through  the  senses  —  is  weakened  by 
drink.  The  ability  of  the  mind  to  associate  or  combine  ideas,  the 
faculty  involved  in  sound  judgment,  showed  that  when  the  persons 
had  taken  the  amounts  of  alcohol  mentioned,  the  combinations  of 
ideas  or  judgments  expressed  by  them  were  confused,  foggy,  senti- 
mental, and  general.     When  the  persons  had  taken  no  alcohol, 


1 


,OfNUDiTIONS 


10  days 

WITHOUT 
alcohol 


BdBijs 


Average  ixme  in  Tninutes 

no  20 30 

f  y  f 


IQrmn.Zsec, 


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alec 


alcohol 


30min48sec 


4£  days 

WITHOUT 
alcohol 


£6  days 
alcokol 


♦ 


Z\yri\nA7sec. 


Z^mnmlGsec, 


The  effect  of  alcohol  upon  ability  to  do  mental  work. 

their  judgments  were  rational,  specific,  keen,  showing  closer  ob- 
servation. 

"  The  words  of  Professor  Helmholtz  at  the  celebration  of  his  seven- 
tieth birthday  are  very  interesting  in  this  connection.  He  spoke  of 
the  ideas  flashing  up  from  the  depths  of  the  unknown  soul,  that 
lies  at  the  foundation  of  every  truly  creative  intellectual  produc- 
tion, and  closed  his  account  of  their  origin  with  these  words : 
'  The  smallest  quantity  of  an  alcoholic  beverage  seemed  to  frighten 
these  ideas  away.'  "  —  Dr.  G.  Sims  Woodhead,  Professor  of  Pa- 
thology, Cambridge  University,  England. 

Professor  Von  Bunge  ( Textbook  of  Physiological  and  Pathological 
Chemistry)  of  Switzerland  says  that :  "  The  stimulating  action 
which  alcohol  appears  to  exert  on  the  brain  functions  is  only  a  para- 


BODY  CONTROL  AND  HABIT  FORMATION      3G7 

lytic  action.  The  cerebral  functions  which  are  first  interfered 
with  are  the  power  of  clear  judgment  and  reason.  •  No  man  ever 
became  witty  by  aid  of  spirituous  drinks.  The  lively  gesticula- 
tions and  useless  exertions  of  intoxicated  people  are  due  to  paraly- 
sis, —  the  restraining  influences,  which  prevent  a  sober  man  from 
uselessly  expending  his  strength,   being  removed. '^ 

The  Drink  Habit.  —  The  harmful  effects  of  alcohol  (aside  from 
the  purely  physiological  effect  upon  the  tissues  and  organs  of  the 
body)  are  most  terribly  seen  in  the  formation  of  the  alcohol  habit. 
The  first  effect  of  drinking  alcoholic  liquors  is  that  of  exhilaration. 
After  the  feeling  of  exhilaration  is  gone,  for  this  is  a  temporary 
state,  the  subject  feels  depressed  and  less  able  to  work  than  before 
he  took  the  drink.  To  overcome  this  feeling,  he  takes  another 
drink.  The  result  is  that  before  long  he  finds  a  habit  formed  from 
which  he  cannot  escape.  With  body  and  mind  weakened,  he 
attempts  to  break  off  the  habit.  But  meanwhile  his  will,  too, 
has  suffered  from  overindulgence.  He  has  become  a  victim  of  the 
drink  habit ! 

"  The  capital  argument  against  alcohol,  that  which  must  even- 
tually condemn  its  use,  is  this,  that  it  takes  away  all  the  reserved 
control,  the  power  of  mastership,  and  therefore  offends  against  the 
splendid  pride  in  himself  or  herself,  which  is  fundamental  in  every 
man  or  woman  worth  anything.'^  —  Dr.  John  Johnson,  quoting 
Walt  Whitman. 

Self-indulgence,  be  it  in  gratification  of  such  a  simple  desire  as 
that  for  candy  or  the  more  harmful  indulgence  in  tobacco  or  al- 
coholic beverages,  is  dangerous  —  not  only  in  its  immediate  effects 
on  the  tissues  and  organs,  but  in  its  more  far-reaching  effects  on 
habit  formation.  Each  one  of  us  is  a  bundle  of  appetites.  If  we 
gratify  appetites  of  the  wrong  kind,  we  are  surely  laying  the 
foundation  for  the  habit  of  excess.  Self-denial  is  a  good  thing 
for  each  of  us  to  practice  at  one  time  or  another,  if  for  no 
other  purpose  than  to  be  ready  to  fight  temptation  when  it 
comes. 

The  Economic  Effect  of  Alcoholic  Poisoning.  —  In  the  struggle 
for  existence,  it  is  evident  that  the  man  whose  intellect  is  the  quick- 
est and  keenest,  whose  judgment  is  most  sound,  is  the  man  who  is 


368      BODY   CONTROL   AND   HABIT   FORMATION 

most  likely  to  succeed.  The  paralyzing  effect  of  alcohol  upon  the 
nerve  centers  must  place  the  drinker  at  a  disadvantage.  In  a 
hundred  ways,  the  drinker  sooner  or  later  feels  the  handicap  that 
the  habit  of  drink  has  imposed  upon  him.  Many  corporations, 
notably  several  of  our  greatest  railroads  (the  Pennsylvania  and 
the  New  York  Central  Railroad  among  them),  refuse  to  employ 
any  but  abstainers  in  positions  of  trust.  Few  persons  know  the 
number  of  railway  accidents  due  to  the  uncertain  eye  of  some  en- 
gineer who  mistook  his  signal,  or  the  hazy  inactivity  of  the  brain 
of  some  train  dispatcher  who,  because  of  drink,  forgot  to  send  the 
telegram  that  was  to  hold  the  train  from  wreck.  In  business  and 
in  the  professions,  the  story  is  the  same.  The  abstainer  wins  out 
over  the  drinking  man. 

Effect  of  Alcohol  on  Ability  to  do  Work.  —  In  Physiological 
Aspects  of  the  Liquor  Problem,  Professor  Hodge,  formerly  of  Clark 
University,  describes  many  of  his  own  experiments  showing  the 
effect  of  alcohol  on  animals.  He  trained  four  selected  puppies  to 
recover  a  ball  thrown  across  a  gymnasium.  To  two  of  the  dogs 
he  gave  food  mixed  with  doses  of  alcohol,  while  the  others  were 
fed  normally.  The  ball  was  thrown  100  feet  as  rapidly  as  recov- 
ered. This  was  repeated  100  times  each  day  for  fourteen  suc- 
cessive days.  Out  of  1400  times  the  dogs  to  which  alcohol  had 
been  given  brought  back  the  ball  only  478  times,  while  the  others 
secured  it  922  times.  " 

Dr.  Parkes  experimented  with  two  gangs  of  men,  selected  to  be  as 
nearly  similar  as  possible,  in  mowing.  He  found  that  with  one 
gang  abstaining  from  alcoholic  drinks  and  the  other  not,  the  ab- 
staining gang  could  accomplish  more.  On  transposing  the  gangs, 
the  same  results  were  repeatedly  obtained.  Similar  results  were 
obtained  by  Professor  Aschaffenburg  of  Heidelberg  University, 
who  found  experimentally  that  men  "  were  able  to  do  15  per  cent 
less  work  after  taking  alcohol." 

Recently  many  experiments  along  the  same  lines  have  been 
made.  In  typewriting,  in  typesetting,  in  bricklaying,  or  in  the 
highest  type  of  mental  work  the  result  is  the  same.  The  quality 
and  quantity  of  work  done  on  days  when  alcohol  is  taken  is  less 
than  on  days  when  no  alcohol  is  taken. 


BODY   CONTROL   AND   HABIT  FORMATION      369 

The  Relation  of  Alcohol  to  Efficiency.  —  We  have  already  seen 
that  work  is  neither  so  well  done  nor  is  as  much  accomplished  by 
drinkers  as  by  non-drinkers. 

A  Massachusetts  shoe  manufacturer  told  a  recent  writer  on 
temperance  that  in  one  year  his  firm  lost  over  $5000  in  shoes 
spoiled  by  drinking  men,  and  that  he  had  himself  traced  these 
spoiled  shoes  to  the  workmen  who,  through  their  use  of  alcoholic 
liquors,  had  thus  rendered  themselves  incapable.  This  is  a  serious 
handicap  to  our  modern  factory  system,  and  explains  why  so  many 
factory  towns  and  cities  are  strongly  favoring  a  policy  of  "  No 
license  "  in  opposition  to  the  saloons. 

''It  is  believed  that  the  largest  number  of  accidents  in  shops  and 
mills  takes  place  on  Monday,  because  the  alcohol  that  is  drunk 
on  Sunday  takes  away  the  skill  and  attentive  care  of  the  work- 
man. To  prove  the  truth  of  this  opinion,  the  accidents  of  the 
building  trades  in  Zurich  were  studied  during  a  period  of  six 
years,  with  the  result  shown  by  this  table  "  :  — 


(From  Tolnian,  Hygiene  for  the  Worker.) 
Shaded,  non-alcoholic ;  black,  alcoholic,  accidents. 


Another  relation  to  efficiency  is  shown  by  the  following  chart. 
During  the  week  the  curve  of  working  efficiency  is  highest  on 
Friday  and  lowest  on  Monday.  The  number  of  accidents  were  also 
least  on  Friday  and  greatest  on  Monday.  Lastly  the  assaults  were 
fewest  in  number  on  Friday  and  greatest  on  Sunday  and  Monday. 
The  moral  is  plain.  Workingmen  are  apt  to  spend  their  week's 
wages  freely  on  Saturday.  Much  of  this  goes  into  drink,  and  as  a 
result  comes  crime  on  Sunday  because  of  the  deadened  moral  and 

HUNTER,    CIV.    BI. 24 


370      BODY   CONTROL   AND   HABIT   FORMATION 


10 

9 

8 

7 
6 

4 
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Notice  that  the  curve  of  efficiency  is  lowest  on  Monday  and  that  crimes  and 
accidents  are  most  frequent  on  Sunday  and  Monday.     Account  for  this. 

mental  condition  of  the  drinker,  and  loss  of  efficiency  on  Monday, 
because  of  the  poisonous  effects  of  the  drug. 

Effect  of  Alcohol  upon  Duration  of  Life.  —  Still  more  serious  is 
the  relation  of  alcohol  as  a  direct  cause  of  disease  (see  table). 

It  is  as  yet  quite  impossible,  in  the  United  States  at  least,  to  tell 
just  how  many  deaths  are  brought  about,  directly  or  indirectly,  by 
alcohol.  Especially  is  this  true  in  trying  to  determine  the  number 
of  cases  of  deaths  from  disease  promoted  by  alcohol.  In  Switzer- 
land provision  is  made  for  learning  these  facts,  and  the  records  of 
that  country  throw  some  light  on  the  subject. 

Dr.  Rudolph  Piister  made  a  studj^  of  the  records  of  the  city  of 
Basle  for  the  years  1892-1906,  finding  the  percentage  of  deaths  in 
which  alcohol  had  been  reported  by  the  attending  physician  as  one 
cause  of  death.     He  found  that  18.1  per  cent  of  all  deaths  of  men 


BODY  CONTROL  AND  HABIT  FORMATION      371 

between  40  and  50  years  of  age  were  caused,  in  part  at  least,  by 
alcohol,  and  this  at  what  should  be  the  most  active  period  in  a 
man's  life,  the  time  when  he  is  most  needed  by  his  family  and 
community.  Taking  all  ages  between  20  and  80,  he  found  that 
alcohol  was  one  cause  of  death  in  one  man  in  every  ten  who  died. 
Another  study  was  made  by  a  certain  doctor  in  Sweden,  from 
records  of  1082  deaths  occurring  in  his  own  practice  and  the  local 
hospital.  No  case  was  counted  as  alcoholic  of  which  there  was  the 
slightest  doubt.  Of  deaths  of  adult  men,  18  in  every  100  were 
due,  directly  or  indirectly,  to  alcoholism.  In  middle  life,  between 
the  ages  of  40  and  50,  29  ;  and  between  50  and  60  years  of  age,  25.6 
out  of  every  100  deaths  had  alcohol  as  one  cause,  thus  agreeing 


15721                                 17418                 ■ 

Alcoholism  +Alcoholic  LiverCirrhosis 

33.139 

22,211                       1 

Typhoid 
~|  2214 

Smallpox 

with  other  statistics  we  have  been  quoting.  —  Fromihe  Metropolitan, 
Vol.  XXV,  Number  11. 

The  Relation  of  Alcohol  to  Crime.  —  A  recent  study  of  more 
than  2500  habitual  users  of  alcohol  showed  that  over  66  per  cent  had 
committed  crime.  Usually  the  crimes  had  been  done  in  saloons 
or  as  a  result  of  quarrels  after  drinking.  Of  another  lot  of  23,581 
criminals  questioned,  20,070  said  that  alcohol  had  led  them  to 
commit  crime. 

The  Relation  of  Alcohol  to  Pauperism.  —  We  have  already 
spoken  of  the  Jukes  family.  These  and  many  other  families  of  a 
similar  sort  are  more  or  less  directly  a  burden  upon  the  state. 
Alcohol  is  in  part  at  least  responsible  for  the  condition  of  such 
families.  Alcohol  weakens  the  efficiency  and  moral  courage,  and 
thus  leads  to  begging,  pauperism,  petty  stealing  or  worse,  and  ul- 


372      BODY  CONTROL  AND   HABIT  FORMATION 


Country 


PERCENTAGE. 
10    20    50    40    50     60    tO     80    90   100 


Belgium 


,N  GLAND 


Fr, 


ANCE 


Germany 


United  5tate5 


Holland 


The  proportion  of  crime  due  to  alcohol  is  shown  in  black. 

timately  to  life  in  some  public  institution.  In  Massachusetts,  of 
3230  inmates  of  such  institutions,  66  per  cent  were  alcoholics. 

The  Relation  of  Alcohol  to  Heredity.  —  Perhaps  the  gravest 
side  of  the  alcohol  question  lies  here.  If  each  one  of  us  had  only 
himself  to  think  of,  the  question  of  alcohol  might  not  be  so  serious. 
But  drinkers  may  hand  down  to  their  unfortunate  children  ten- 
dencies toward  drink  as  well  as  nervous  diseases  of  various  sorts ; 
an  alcoholic  parent  may  beget  children  who  are  epileptic,  neu- 
rotic, or  even  insane. 

In  the  State  of  New  York  there  are  at  the  present  time  some 
30,000  insane  persons  in  public  and  private  hospitals.  It  is  be- 
lieved that  about  one  fifth  of  them,  or  6000  patients,  owe  their 
insanity  to  alcohol  used  either  by  themselves  or  by  their  parents. 
In  the  asylums  of  the  United  States  there  are  150,000  insane  people. 
Taking  the  same  proportions  as  before,  there  are  30,000  persons 
in  this  country  whom  alcohol  has  made  or  has  helped  to  make 
insane.     This  is  the  most  terrible  side  of  the  alcohol  problem. 

Refebence  Reading 
elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.    American  Book  Company. 

Overton,  General  Hygiene.     American  Book  Company. 

The  Gulick  Hygiene  Series,  Emergencies,  Good  Health,  The  Body  at  Work,  Control 

of  Body  and  Mind.     Ginn  and  Company. 
Ritchie,  Human  Physiology.     World  Book  Company. 
Hough  and  Sedgwick,  The  Human  Mechanism.     Ginn  and  Company. 


XXIV.  MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT 

Problems,  — How  may  ive  improve  our  home  conditions  of 
living  ? 

How  may  we  help  improve  our  conditions  at  school? 

How  does  the  city  care  for  the  improvement  of  our  environ- 
ment ? 

(a)  In  inspection  of  buildings,  etc. 

(&)  In  inspection  of  food  supplies. 

(c)  In  inspection  of  milh. 

(d)  In  care  of  water  supplies. 

(e)  In  disposal  of  wastes. 
(/)  In  care  of  public  health. 

Laboratory  Suggestions 

Home  exercise.  —  How  to  ventilate  my  bedroom. 

Demonstration. —  Effect  of  use  of  duster  and  damp  cloth  upon  bacteria 
in  schoolroom. 

Home  exercise.  —  Luncheon  dietaries. 

Home  exercise.  —  Sanitary  map  of  my  own  block. 

Demonstration.  —  The  bacterial  content  of  milk  of  various  grades  and 
from  different  sources. 

Demonstration.  —  Bacterial  content  of  distilled  water,  rain  water,  tap 
water,  dilute  sewage. 

Laboratory  exercise.  —  Study  of  board  of  health  tables  to  plot  curves 
of  mortality  from  certain  diseases  during  certain  times  of  year. 

The  Purpose  of  this  Chapter.  —  In  the  preceding  chapters  we 
have  traced  the  lives  of  both  plants  and  animals  within  their  own 
environment.  We  have  seen  that  man,  as  well  as  plants  and  other 
animals,  needs  a  favorable  environment  in  order  to  live  in  comfort 
and  health.  It  will  be  the  purpose  of  the  following  pages  first  to 
show  how  we  as  individuals  may  better  our  home  environment, 
and  secondly,  to  see  how  we  may  aid  the  civic  authorities  in  the 
betterment  of  conditions  in  the  city  in  which  we  live. 

373 


374    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 


How  I  should  ventilate  my  bed- 
room. 


Home  Conditions.  —  The  Bedroom.  —  We  spend  about  one 
third  of  our  total  time  in  our  bedroom.  This  room,  therefore, 
deserves  more  than  passing  attention.     First  of  all,  it  should  have 

good  ventilation.  Two  windows 
make  an  ideal  condition,  especially 
if  the  windows  receive  some  sun. 
Such  a  condition  as  this  is  mani- 
festly impossible  in  a  crowded  city, 
where  too  often  the  apartment 
bedrooms  open  upon  narrow  and 
ill-ventilated  courts.  Until  com- 
paratively recent  time,  tenement 
houses  were  built  so  that  the  bed- 
rooms had  practically  no  light  or 
air ;  now,  thanks  to  good  tenement- 
house  laws,  wide  airshafts  and  larger  windows  are  required  by 
statute. 

Care  of  the  Bedroom.  —  Since  sunlight  cannot  always  be  ob- 
tained for  a  bedroom,  we  must  so  care  for  and  furnish  the  room 
that  it  will  be  difficult  for  germs  to  grow  there.  Bedroom  furni- 
ture should  be  light  and  easy  to  clean,  the  bedstead  of  iron,  the 
floors  painted  or  of  hardwood.  No  hangings  should  be  allowed 
at  the  windows  to  collect  dust,  nor  should  carpets  be  allowed  for 
the  same  reason.  Rugs  on  the  floor  may  easily  be  removed  when 
cleaning  is  done.  The  furniture  and  woodwork  should  be  wiped 
with  a  damp  cloth  every  day.  Why  a  darnp  cloth?  In  certain 
tenements  in  New  York  City,  tuberculosis  is  believed  to  have  been 
spread  by  people  occupying  rooms  in  which  a  previous  tenant  has 
had  tuberculosis.  A  new  tenant  should  insist  on  a  thorough  clean- 
ing of  the  bedrooms  and  removal  of  old  wall  paper  before  occu- 
pancy. 

Sunlight  Important.  —  In  choosing  a  house  in  the  country  we 
would  take  a  location  in  which  the  sunlight  was  abundant.  A 
shaded  location  might  be  too  damp  for  health.  Sunlight  should 
enter  at  least  some  of  the  rooms.  In  choosing  an  apartment  we 
should  have  this  matter  in  mind,  for,  as  we  know,  germs  cannot 
long  exist  in  sunlight. 


MAN'S   IMPROVEMENT   OF   HIS   ENVIRONMENT    375 


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This  map  shows  how  cases  of  tuberculosis  are  found  recurring  in  the  same  locality 
and  in  the  same  houses  year  after  year.  Each  black  dot  is  one  case  of  tubercu- 
losis. 

Heating.  — ■  Houses  in  the  country  are  often  heated  by  open 
fires,  stoves  or  hot-air  furnaces,  all  of  which  make  use  of  heated 
currents  of  air  to  warm  the  rooms.  But  in  the  city  apartments, 
usually  pipes  conduct  steam  or  hot  water  from  a  central  plant  to  our 
rooms.     The  difficulty  with  this  system  is  that  it  does  not  give  us 


376    MAN'S   IMPROVEMENT  OF  HIS  ENVIRONMENT 

fresh  air,  but  warms  over  the  stale  air  in  a  room.  Steam  causes 
our  rooms  to  be  too  warm  part  of  the  time,  and  not  warm  enough 
part  of  the  time.  Thus  we  become  overheated  and  then  take  cold 
by  becoming  chilled.  Steam  heat  is  thus  responsible  for  much 
sickness. 

Lighting.  —  Lighting  our  rooms  is  a  matter  of  much  importance. 
A  student  lamp,  or  shaded  incandescent  light,  should  be  used  for 
reading.  Shades  must  be  provided  so  that  the  eyes  are  protected 
fiom  direct  light.  Gas  is  a  dangerous  servant,  because  it  contains 
a  very  poisonous  substance,  carbon  monoxide.  ''It  is  estimated 
that  14  per  cent  of  the  total  product  of  the  gas  plant  leaks  into  the 
streets  and  houses  of  the  cities  supplied."  This  forms  an  unseen 
menace  to  the  health  in  cities.  Gas  pipes,  and  especially  gas  cocks, 
should  be  watched  carefully  for  escaping  gas.  Rubber  tubing 
should  not  be  used  to  conduct  gas  to  movable  gas  lamps,  because 
it  becomes  worn  and  allows  gas  to  escape. 

Insects  and  Foods.  —  In  the  summer  our  houses  should  be  pro- 
vided with  screens.     All  food  should  be  carefully  protected  from 


During  the  summer  all  food  should  be  protected  from  flies.     Why  ? 

flies.  Dirty  dishes,  scraps  of  food,  and  such  garbage  should  be 
quickly  cleaned  up  and  disposed  of  after  a  meal.  Insect  powder 
(pyrethrum)  will  help  keep  out  ''croton  bugs"  and  other  undesir- 
able household  pests,  but  cleanliness  will  do  far  more.  Most 
kitchen  pests,  as  the  roach,  simply  stay  with  us  because  they  find 
dirt  and  food  abundant. 


MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT    377 


Use  of  Ice.  —  Food  should  be  properly  cared  for  at  all  times,  but 
especially  during  the  summer.  Iceboxes  are  a  necessity,  especially 
where  children  live,  in  order  to  keep  milk  fresh.  A  dirty  icebox 
is  almost  as  bad  as  none  at  all,  because  food  will  decay  or  take  on 
unpleasant  odors  from  other  foods. 

Disposal  of  Wastes.  —  In  city  houses  the  disposal  of  human 
wastes  is  provided  for  by 
a  city  system  of  sewers. 
The  wastes  from  the  kit- 
chen, the  garbage,  should 
be  disposed  of  each  day. 
The  garbage  pail  should 
be  frequently  sterilized  by 
rinsing  it  with  boiling 
water.  Plenty  of  lye  or 
soap  should  be  used.  Re- 
member that  flies  frequent 
the  uncovered  garbage 
pail,  and  that  they  may 
next  walk  on  your  food. 
Collection  and  disposal  of 
garbage  is  the  work  of  the 
municipality. 

School  Surroundings.  — 
How  to  Improve  Them.  — 
From  five  to  six  hours  a 
day  for  forty  weeks  is 
spent  by  the  average  boy 

or  girl  in  the  schoolroom.  It  is  part  of  our  environment  and  should 
therefore  be  considered  as  worthy  of  our  care.  Not  only  should 
a  schoolroom  be  attractive,  but  it  should  be  clean  and  sanitary. 
City  schools,  because  of  their  locations,  of  the  sometimes  poor  jani- 
torial service,  and  especially  because  of  the  selfishness  and  care- 
lessness of  children  who  use  them,  may  be  very  dirty  and  unsani- 
tary. Dirt  and  dust  breed  and  carry  bacteria.  Plate  cultures 
show  greatly  increased  numbers  of  bacteria  to  be  in  the  air  when 
pupils  are  moving  about,  for  then  dust,  bearing  bacteria,  is  stirred  up 


The  wrong  and  the  right  kind  of  garbage  cans. 


378    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 

and  circulated  through  the  air.  Sweeping  and  dusting  with  dry 
brooms  or  feather  dusters  only  stirs  up  the  dust,  leaving  it  to  settle 
in  some  other  place  with  its  load  of  bacteria.  Professor  Hodge 
tells  of  an  experience  in  a  school  in  Worcester,  Mass.  A  health 
brigade  was  formed  among  the  children,  whose  duty  was  to  clean 
the  rooms  every  morning  by  wiping  all  exposed  surface  with  a  damp 


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The  culture  (A)  was  exposed  to  the  air  of  a  dirty  street  in  the  crowded  part  of 
Manhattan.  (B)  was  exposed  to  the  air  of  a  well-cleaned  and  watered  street  in 
the  uptown  residence  portion.  Which  culture  has  the  more  colonies  of  bac- 
teria ?     How  do  you  account  for  this  ? 


cloth.  In  a  school  of  425  pupils  not  a  single  case  of  contagious 
diseases  appeared  during  the  entire  year.  Why  not  try  this  in 
your  own  school  ? 

Unselfishness  the  Motto.  —  Pupils  should  be  unselfish  in  the 
care  of  a  school  building.  Papers  and  scraps  dropped  by  some 
careless  boy  or  girl  make  unpleasant  the  surroundings  for  hundreds 
of  others.  Chalk  thrown  by  some  mischievous  boy  and  then 
tramped  underfoot  may  irritate  the  lungs  of  a  hundred  innocent 
schoolmates.  Colds  or  worse  diseases  may  be  spread  through 
the  filthy  habits  of  some  boys  who  spit  in  the  halls  or  on  the 
stairways. 

Lunch  Time  and  Lunches.  —  If  you  bring  your  own  lunch  to 
school,  it  should  be  clean,  tasty,  and  well  balanced  as  a  ration.  In 
most  large  schools  well-managed  lunch  rooms  are  part  of  the  school 


MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT    379 


^^,_« 


A  sensible  lunch  box,  sanitary 
and  compact. 


equipment,  and  balanced  lunches  can  be  obtained  at  low  cost. 

Do  not  make  a  lunch  entirely  from  cold  food,  if  hot  can  be  obtained. 

Do  not  eat  only  sweets.     Ice  cream  is  a  good  food,  if  taken  with 

something  else,  but  be  sure  of  your  ice 

cream.    "  Hokey  pokey  "  cream,  tested 

in   a   New    York    school    laboratory, 

showed  the   presence   of  many   more 

colonies   of   bacteria   than   good   milk 

would  show.     Above  all,  be  sure  the 

food  you  buy  is  clean.     Stands  on  the 

street,   exposed    to    dust    and    germs, 

often  sell  food  far  from  fit  for  human 

consumption. 

If  you  eat  your  lunch  on  the  street 

near  your    school,    remember   not   to 

scatter  refuse.     Paper,  bits  of  lunch, 

and  the  like  scattered  on  the  streets  around  your  school  show  lack 

of  school  spirit  and  lack  of  civic  pride.     Let  us  learn  above  all 

other  things  to  be  good  citizens. 

Inspection  of  Factories,  Public  Buildings,  etc.  —  It  is  the  duty 

of  a  city  to  inspect  the  condition 
of  all  public  buildings  and  espe- 
cially of  factories.  Inspection 
should  include,  first,  the  super- 
vision of  the  work  undertaken. 
Certain  trades  where  grit,  dirt, 
or  poison  fumes  are  given  off 
are  dangerous  to  human  health, 
hence  care  for  the  workers  be- 
comes a  necessity.  Factories 
should  also  be  inspected  as  to 
cleanliness,  the  amount  of  air 
space  per  person  employed, 
ventilation,  toilet  facilities,  and 
proper  fire  protection.  Tene- 
ment    inspection     should     be 

thorough  and  should  aim  to  provide  safe  and  sanitary  homes. 


Dust  exhausts  on  grinding  wheels  protect 
lungs  of  the  workmen. 


380    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 


Inspection  of  Food  Supplies.  —  In  a  city  certain  regulations  for 
the  care  of  public  supplies  are  necessary.  Foods,  both  fresh  and 
preserved,  must  be  inspected  and  rendered  safe  for  the  thousands 
of  people  who  are  to  use  them.  All  raw  foods  exposed  on  stands 
should  be  covered  so  as  to  prevent  insects  or  dust  laden  with 
bacteria  from  coming  in  contact  with  them.  Meats  must  be  in- 
spected for  diseases,  such  as  tuberculosis  in  beef,  or  trichinosis  in 
pork.  Cold  storage  plants  must  be  inspected  to  prevent  the  keep- 
ing of  food  until  it  becomes  unfit  for  use.  Inspection  of  sanitary 
conditions  of  factories  where  products  are  canned,  or  bakeries 
where  foods  are  prepared,  must  be  part  of  the  work  of  a  city  in 
caring  for  its  citizens. 

Care  of  Raw  Foods.  —  Each  one  of  us  may  cooperate  with  the 
city  government  by  remembering  that  fruits  and  vegetables  can 
be  carriers  of  disease,  especially  if  they  are  sold  from  exposed  stalls 
or  carts  and  handled  by  the  passers-by.  All  vegetables,  fruits,  or 
raw  foods  should  be  carefully  washed  before  using.  Spoiled  or 
overripe  fruit,  as  well  as  meat  which  is  decayed,  is  swarming  with 
bacteria  and  should  not  be  used. 

An  interesting  exercise  would  be  the  inspection  of  conditions 
in  your  own  home  block.  Make  a  map  showing  the  houses  on  the 
block.  Locate  all  stores,  saloons,  factories,  etc.  Notice  any  cases 
of  contagious  disease,  marking  this  fact  on  the  map.  Mark  all 
heaps  of  refuse  in  the  street,  all  uncovered  garbage  pails,  any  street 

stands  that  sell  uncovered 
fruit,  and  any  stores  with 
an  excessive  number  of 
flies. 

In  addition  to  food  in- 
spection, two  very  impor- 
tant supplies  must  be  ren- 
dered safe  by  a  city  for  its 
citizens.  These  are  milk 
and  water. 

Care    in   Production   of 
^,  •     ,      ,  -.u  ,  n  J      Milk.  —  Milk  when  drawn 

Clean  cows  in  clean  barns  with  clean  milkers  and 
clean  milk  pails  means  clean  milk  in  the  city.         from  a  healthy  COW  should 


MAN'S   IMPROVEMENT  OF  HIS  ENVIRONMENT    381 

be  free  from  bacteria.  But  immediately  on  reaching  the  air  it 
may  receive  bacteria  from  the  air,  from  the  hands  of  the  person 
who  milks  the  cows,  from  the  pail,  or  from  the  cow  herself.  Cows 
should,  therefore,  be  milked  in  surroundings  that  are  sanitary, 
the  milkers  should  wear  clean  garments,  put  on  over  their  ordinary 
clothes  at  milking  time,  while  pails  and  all  utensils  used  should 
be  kept  clean.  Especially  the  surface  exposed  on  the  udder  from 
which  the  milk  is  drawn  should  be  cleansed  before  milking. 

Most  large  cities  now  send  inspectors  to  the  farms  from  which 
milk  is  supplied.  Farms  that  do  not  accept  certain  standards  of 
cleanliness  are  not  allowed  to  have  their  milk  become  part  of  the 
city  supply. 

Tuberculosis  and  Milk.  —  It  is  recognized  that  in  some  Euro- 
pean countries  from  30  to  40  per  cent  of  all  cattle  have  tuberculosis. 
Many  dairy  herds  in  this  country  are  also  infected.  It  is  also 
known  that  the  tubercle  bacillus  of  cattle  and  man  are  much 
ahke  in  form  and  action  and  that  the  germ  from  cattle  would 
cause  tuberculosis  in  man.  Fortunately,  the  tuberculosis  germ 
does  not  groiv  in  milk,  so  that  even  if  milk  from  tubercular  cattle 
should  get  into  our  supply,  it  would  be  diluted  with  the  milk  of 
healthy  cattle.  In  order  to  protect  our  milk  supply  from  these 
germs  it  would  be  necessary  to  kill  all  tubercular  cattle  (almost  an 
impossibility)  or  to  pasteurize  our  milk  so  as  to  kill  the  germs  in  it. 

Other  Disease  Germs  in  Milk.  —  We  have  already  shown 
how  typhoid  may  be  spread  through  milk.  Usually  such  out- 
breaks may  be  traced  to  a  single  case  of  typhoid,  often  a  person 
who  is  a  ''  typhoid  carrier,"  i.e.  one  who  may  not  suffer  from  the 
effects  of  the  disease,  but  who  carries  the  germs  in  his  body,  spread- 
ing them  by  contact.  A  recent  epidemic  of  typhoid  in  New  York 
City  was  traced  to  a  single  typhoid  carrier  on  a  farm  far  from  the 
city.  Sometimes  the  milk  cans  may  be  washed  in  contaminated 
water  or  the  cows  may  even  get  the  germs  on  their  udders  by  wad- 
ing in  a  polluted  stream.  Diphtheria,  scarlet  fever,  and  Asiatic 
cholera  are  also  undoubtedly  spread  through  milk  supplies.  Milk 
also  plays  a  very  important  part  in  the  high  death  rate  from  diar- 
rheal diseases  among  young  children  in  warm  weather.     Why? 

Grades  of  Milk  in  a  City  Supply.  —  Milk  which  comes  to  a  city 


382    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 


J  L 


J  L 


J   L 


j]      t«ii»«n«iiitJ      ka 


[ 


A  diagram  to  show  how  typhoid  may  be  spread  in  a  city  through  an  infected  milk 
supply.  The  black  spots  in  the  blocks  mean  cases  of  typhoid.  A,  a  farm 
where  typhoid  exists ;  the  dashes  in  the  streets  represent  the  milk  route.  B  is 
a  second  farm  which  sends  part  of  its  milk  to  A  ;  the  milk  cans  from  B  are 
washed  at  farm  A  and  sent  back  to  B.  A  few  cases  of  typhoid  appear  along 
B's  milk  route.     How  do  you  account  for  that  ? 

may  be  roughly  placed  in  three  different  classes.  The  best  milk, 
coming  from  farms  where  the  highest  sanitary  standards  exist, 
where  the  cows  are  all  tubercular  tested,  where  modern  appliances 
for  handling  and  cooling  the  milk  exist,  is  known  as  certified  or,  in 
New  York  City,  grade  A  milk.  Most  of  the  milk  sold,  however, 
is  not  so  pure  nor  is  so  much  care  taken  in  handling  it.  Such  milk, 
known  in  New  York  as  grade  B  milk,  is  pasteurized  before  de- 
livery, and  is  sold  only  in  bottles.  A  still  lower  grade  of  milk 
(dipped  milk)  is  sold  direct  from  cans.  It  is  evident  that  such 
milk,  often  exposed  to  dust  and  other  dirt,  is  unfit  for  any  purpose 
except  for  cooking.  It  should  under  no  circumstances  be  used  for 
children.     A  regulation  recently  made  by  the  New  York  City 


MAN'S   IMPROVEMENT   OF   HIS   ENVIRONMENT     383 


Department  of  Health  states  that  milk  sold  ''  loose  "  in  restaurants, 
lunch-rooms,  soda  fountains,  and  hotels  must  be  pasteurized. 

Care  of  a  City  Milk  Supply.  —  Besides  caring  for  milk  in  its 
production  on  the  farm,  proper  transportation  facilities  must  be 
provided.  Much  of  the  milk  used  in  New  York  City  is  forty-eight 
hours  old  before  it  reaches  the  consumer.  During  shipment  it 
must  be  kept  in  refrigerator  cars,  and  during  transit  to  customers  it 
should  be  iced.  Why?  All  but  the  highest  grade  milk  should  be 
pasteurized.  Why?  Milk  should  be  bottled  by  machinery  if 
possible  so  as  to  insure  no  personal  contact ;  it  should  be  kept  in 
clean,  cool  places ;  and  no  milk  should  be  sold  by  dipping  from 
cans.     Why  is  this  a  method  of  dispensing  impure  milk? 

Care  of  Milk  in  the  Home.  —  Finally,  milk  at  home  should  re- 
ceive the  best  of  care.  It  should  be  kept  on  ice  and  in  covered 
bottles,  because  it  readily 
takes  up  the  odors  of  other 
foods.  If  we  are  not  cer- 
tain of  its  purity  or  keep- 
ing qualities,  it  should  be 
pasteurized  at  home. 
Why? 

Water  Supplies.  —  One 
of  the  greatest  assets  to 
the  health  of  a  large  city 
is  pure  water.  By  pure 
water  we  mean  water  free 
from  all  organic  impurities, 
including  germs.  Water 
from  springs  and  deep 
driven  wells  is  the  safest 
water,  that  from  large 
reservoirs  next  best,  while 
water  that  has  drainage 
in  it,  river  water  for  ex- 
ample, is  very  unsafe. 

The  waters  from  deep 
wells  or  springs  if  properly 


New  York  City  is  spending  8350,000,000  to 
have  a  pure  and  abundant  water  supply. 
This  is  the  tunnel  which  will  bring  the 
water  from  the  Catskill  Mountains  to  New 
York  City. 


384    MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT 


protected  will  contain  no  bacteria.  Water  taken  from  protected 
streams  into  which  no  sewage  flows  will  have  but  few  bacteria,  and 
these  will  be  destroyed  if  exposed  to  the  action  of  the  sun  and  the 
constant  aeration  (mixing  with  oxygen)  which  the  surface  water 
receives  in  a  large  lake  or  reservoir.     But  water  taken  from  a  river 


ORIGINAL  CASES  IN 

NORTH    OCLMSrORO 


FCSULTtNG   CA^r.     -^ 


I8»l. 


The  city  of  Lowell  in  1891  took  its  water  without  filter i7ig,  i.e.  from  the  Merrimack 

River  at  the  point  shown  on  the  map. 
Typhoid  fever  broke  out  in  North  Chelmsford  and  about  two  weeks  later  cases 

began  to  appear  in  Lowell  until  a  great  epidemic  occurred.      Explain  this 

outbreak.     Each  black  dot  is  a  case  of  typhoid. 

into  which  the  sewage  of  other  towns  and  cities  flows  must  be 
filtered  before  it  is  fit  for  use. 

Typhoid  fever  germs  live  in  the  food  tube,  hence  the  excreta  of 
a  typhoid  patient  will  contain  large  numbers  of  germs.  In  a  city 
with  a  system  of  sewage  such  germs  might  eventually  pass  from 
the  sewers  into  a  river.  Many  cities  take  their  water  supply 
directly  from  rivers,  sometimes  not  far  below  another  large  town. 
Such  cities  must  take  many  germs  into  their  water  supply.  Many 
cities,  as  Cleveland  and  Buffalo,  take  their  water  from  lakes  into 
which  their  sewage  flows.  Others,  as  Albany,  Pittsburgh,  and  Phila- 
delphia, take  their  drinking  water  directly  from  rivers  into  which 


MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT     385 


I 

*^| 

iff  L,|  jjagfetiiiB^iiife'                         ^^^1 

Filter  beds  at  Albany,  N.  Y. 


sewage  from  cities  above  them  on  the  river  has  flowed.  Filter- 
ing such  water  by  means  of  passing  the  water  through  settling 
basins  and  sand  filters  removes  about  98  per  cent  of  the  germs.  The 
result  of  drinking  unfiltered  and  filtered  water  in  certain  large  cities 
is  shown  graph- 
ically at  right. 
In  cities  which 
drain  their  sewage 
into  rivers  and 
lakes,  the  question 
of  sewage  disposal 
is  a  large  one,  and 
many  cities  now 
have  means  of  dis- 
posing of  their  sew- 
age in  some  man- 
ner as  to  render  it 
harmless  to  their 
neighbors. 

Railroads  are  often  responsible  for  carrying  typhoid  and  spread- 
ing it.  It  is  said  that  a  recent  outbreak  of  typhoid  in  Scranton, 
Fa.,  was  due  to  the  fact  that  the  excreta  from  a  typhoid  patient 
traveling  in  a  sleeping  car  was  washed  by  rain  into  a  reservoir  near 
which  the  train  was  passing.  Railroads  are  thus  seen  to  be  great 
open  sewors.     A  sanitary  car  toilet  is  the  only  remedy. 

HUNTER,    CIV.    BI. 25 


f 

A  ( 

1 1- 1 1         I         1 1 1 1         1         1 

20        4.0        6O         6O        100      120       140       160       180      200    220 

1904 

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^^ 

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^^ 

^^ 

1901 

W//M 

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p////(/l 

V 

Cases  of  typhoid  per  100,000  inhabitants  before  filtering 
water  supply  (solid)  and  after  (shaded)  in  A,  Water- 
town,  N.Y.;  Z?,  Albany,  N .  Y. ;  C,  Lawrence,  Mass.: 
D,  Cincinnati,  Ohio.  What  is  the  effect  of  filtering 
the  water  supply  ? 


386     MAN'S   niPROVEMEXT   OF   HIS   ENVIRONMENT 


//  \.\fBI  7i( ■      r./Ji.  1/  !. \'> ' 

wAiLii  .SI  /'/'LY  .-Kxn  ciira.rji.A 


AJLTOSA 

A-tls. 

-:-! 

^  ■  ^ 

//  1  1//.  (  Kf, 


•"*  — 


This  chart  shows  that  during  a  cholera  epidemic  in  1892  there  were  hundreds 
of  cases  of  cholera  in  Hamburg,  which  used  unfiltered  water  from  the  Elbe, 
but  in  adjoining  Altona,  where  filtered  water  was  used,  the  cases  were 
very  few. 

Sewage  Disposal.  —  Sewage  disposal  is  an  important  sanitary 
problem  for  any  city.  Some  cities,  like  New  York,  pour  their 
sewage  directly  mto  rivers  which  flow  into  the  ocean.  Conse- 
quently much  of  the  liquid  which  bathes  the  shores  of  Manhattan 
Island  is  dilute  sewage.  Other  cities,  like  Buffalo  or  Cleveland,  send 
their  sewage  into  the  lakes  from  which  they  obtain  their  supply  of 
drinking  water.  Still  other  cities  which  are  on  rivers  are  forced  to 
dispose  of  their  sewage  in  various  ways.     Some  have  a  system  of 


Stone  filter  beds  in  a  sewage  disposal  plant. 


MAN'S   IMPROVEMENT  OF  HIS   ENVIRONMENT    387 


filter  beds  in  which  the  solid  wastes  are  acted  upon  by  the  bacteria 
of  decay,  so  that  they  can  be  collected  and  used  as  fertilizer. 
Others  precipitate  or  condense  the  solid  materials  in  the  sewage 
and  then  dispose  of  it.  Another  method  is  to  flow  the  sewage  over 
large  areas  of  land,  later  using  this  land  for  the  cultivation  of  crops. 
This  method  is  used  by  many  small  European  cities. 

The  Work  of  the  Department  of  Street  Cleaning.  —  In  any 
city  a  menace  to  the  health  of  its  citizens  exists  in  the  refuse  and 
garbage.  The  city  streets,  when  dirty,  contain  countless  millions 
of  germs  which  have  come  from  decaying  material,  or  from  people 
ill  with  disease.  In  most 
large  cities  a  department 
of  street  cleaning  not  only 
cares  for  the  removal  of 
dust  from  the  streets,  but 
also  has  the  removal  of 
garbage,  ashes,  and  other 
waste  as  a  part  of  its 
work.  The  disposal  of 
solid  wastes  is  a  tremen- 
dous task.  In  Manhattan  the  dry  wastes  are  estimated  to  be 
1,000,000  tons  a  year  in  addition  to  about  175,000  tons  of  garbage. 
Prior  to  1895  in  the  city  of  New  York  garbage  was  not  separated 
from  ashes  ;  now  the  law  requires  that  garbage  be  placed  in  separate 
receptacles  from  ashes.  Do  you  see  why?  The  street-cleaning 
department  should  be  aided  by  every  citizen ;  rules  for  the  separa- 
tion of  garbage,  papers,  and  ashes  should  be  kept.  Garbage  and 
ash  cans  should  be  covered.  The  practice  of  upsetting  ash  or  gar- 
bage cans  is  one  which  no  young  citizen  should  allow  in  his  neigh- 
borhood, for  sanitary  reasons.  The  best  results  in  summer  street 
cleaning  are  obtained  by  washing  or  flushing  the  streets,  for  thus 
the  dirt  containing  germs  is  prevented  from  getting  into  the  air. 
The  garbage  is  removed  in  carts,  and  part  of  it  is  burned  in  huge 
furnaces.  The  animal  and  plant  refuse  is  cooked  in  great  tanks ; 
from  this  material  the  fats  are  extracted,  and  the  solid  matter  is 
sold  for  fertilizer.  Ashes  are  used  for  filling  marsh  land.  Thus 
the  removal  of  waste  matter  may  pay  for  itself  in  a  large  city. 


Collecting  ashes. 


388    MAN'S  IMPROVEMENT  OF  HIS   ENVIRONMENT 


An  Experiment  in  Civic  Hygiene.  —  During  the  summer  of  1913 
an  interesting  experiment  on  the  relation  of  flies  and  filth  to  disease 
was  carried  on  in  New  York  City  by  the  Bureau  of  Public  Health 
and  Hygiene  of  the  New  York  Association  for  improving  the  con- 
dition of  the  poor. 
Two  adjoining  blocks 
were  chosen  in  a 
thickly  populated  part 
of  the  Bronx  near  a 
number  of  stables 
which  were  the 
sources  of  great  num- 
bers of  flies.  In  one 
block  all  houses  were 
screened,  garbage  pails 
were  furnished  with 
covers,  refuse  was  re- 
moved and  the  sur- 
roundings made  as 
sanitary  as  possible. 
In  the  adjoining  block 
conditions  were  left 
unchanged.  During 
the  summer  as  flies 
began  to  breed  in  the 
manure  heaps  near  the 
stables  all  manure  was 

disiTifepted  T^hns  the 
The  upper  picture  shows  the  stables  where  millions 

of  flies  were  bred ;  the  lower  picture,  the  disinfec-      breeding    of    flieS    WaS 

tion  of  manure  so  as  to  prevent  the  breeding  of      checked         The     cam- 

paign  of  education  was 
continued  during  the  summer  by  means  of  moving  pictures, 
nurses,  boy  scouts,  and  school  children  who  became  interested. 

At  the  end  of  the  summer  it  was  found  that  there  had  been  a 
considerable  decrease  in  the  number  of  cases  of  fly-carried  diseases 
and  a  still  greater  decrease  in  the  total  days  of  sickness  (especially 
of  children)  in  the  screened  and  sanitary  block.    The  table  and 


MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT    389 


pictures  speak  for  themselves.  If  such  a  small  experiment  shows 
results  like  this,  then  what  might  a  general  cleanup  of  a  city  show  ? 

Public  Hygiene.  —  Although  it  is  absolutely  necessary  for  each 
individual  to  obey  the  laws  of  health  if  he  or  she  wishes  to  keep 
well,  it  has  also  be- 
come necessary,  espe- 
cially in  large  cities, 
to  have  general  super- 
vision over  the  health 
of  people  living  in  a 
community.  This  is 
done  by  means  of  a 
department  or  board 
of  health.  It  is  the 
function  of  this  de- 
partment to  care  for 
public  health.  In  ad- 
dition to  such  a  body 
in  cities,  supervision 
over  the  health  of  its 
citizens  is  also  exer- 
cised by  state  boards 
of  health.  But  as  yet 
the  government  of  the 
United  States  has  not 
established  a  Bureau 
of  Health,  important 
as  such  a  bureau 
would  be. 

The  Functions  of  a 
City  Board  of  Health. 
—  The  administration 

of  the  Board  of  Health  in  New  York  City  includes  a  number  of 
divisions,  each  of  which  has  a  different  work  to  do.  Each  is  in 
itself  important,  and,  working  together,  the  entire  machine  provides 
ways  and  means  for  making  the  great  city  a  safe  and  sanitary 
place  in  which  to  live.     Let  us  take  up  the  work  of  each  division 


In  the  upper  picture  a  little  girl  can  be  seen  dump- 
ing garbage  from  the  fire  escape.  She  was  a 
foreigner  and  knew  no  better.  The  picture  below 
shows  the  result  of  such  garbage  disposal. 


390    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 

of  the  health  board  in  order  to  find  out  how  we  may  cooperate  with 
them. 

The  Division  of  Infectious  Diseases.  —  Infectious  diseases  are 
chiefly  spread  through  personal  contact.  It  is  the  duty  of  a  gov- 
ernment to  prevent  a  person  having  such  a  disease  from  spreading 
it  broadcast  among  his  neighbors.  This  can  be  done  by  quarantine 
or  isolation  of  tlie  person  having  the  disease.  So  the  board  of 
health  at  once  isolates  any  case  of  disease  which  may  be  communi- 


DI5EASFS 

FILTHY  AREA 

CLEANED-UPAREA 

TOTAL 
5ICKNE55 

165                   1 

MO            1 

COMMUNI  CABLC  ^tUSM 

36  1 

COMMUNICABLE 

lEB^^^^H 

74        1 

POSSIBLY     j^vq^VH 

FLY- BORNE  P*a2^B 

m 

Comparison  of  cases  of  illness  during  the  summer  of  1913  in  two  city  blocks,  one 
clean  and  the  other  dirty.     What  are  your  conclusions  ? 


cated  from  one  person  to  another.  No  one  save  the  doctor  or 
nurse  should  enter  the  room  of  the  person  quarantined.  After 
the  disease  has  run  its  course,  the  clothing,  bedding,  etc.,  in  the 
sick  room  is  fumigated.  This  is  usually  done  by  the  board  of 
health.  Formaldehyde  in  the  form  of  candles  for  burning  or  in  a 
liquid  form  is  a  good  disinfectant.  In  disinfecting  the  room  should 
be  tightly  closed  to  prevent  the  escape  of  the  gas  used,  as  the 
object  of  the  disinfection  is  to  kill  all  the  disease  germs  left  in  the 
room.  In  some  cases  of  infectious  disease,  as  scarlet  fever,  it  is 
found  best  to  isolate  the  patients  in  a  hospital  used  for  that  pur- 
pose. Examples  of  the  most  infectious  diseases  are  measles, 
scarlet  fever,  whooping  cough,  and  diphtheria. 

Immunity.  —  In  the  prevention  of  germ  diseases  we  must  fight 
the  germ  by  attacking  the  parasites  directly  with  poisons  that  will 
kill  them  (such  poisons  are  called  germicides  or  disinfectants) ,  and 
we  must  strive  to  make  the  persons  coming  in  contact  with  the 
disease  unlikely  to  take  it.     This  insusceptibility  or  immunity  may 


MAN'S   IMPROVEMENT  OF  HIS   ENVIRONMENT    391 

be  either  natural  or  acquired.  Natural  immunity  seems  to  be  in 
the  constitution  of  a  person,  and  may  be  inherited.  Immunity 
may  be  acquired  by  means  of  such  treatment  as  the  antitoxin 
treatment  for  diphtheria.  This  treatment,  as  the  name  denotes, 
is  a  method  of  neutralizing  the  poison  (toxin)  caused  by  the  bacteria 
in  the  system.  It  was  discovered  a  few  years  ago  by  a  German, 
Von  Behring,  that  the  serum  of  the  blood  of  an  animal  immune 
to  diphtheria  is  capable  of  neutralizing  the  poison  produced  by 
the  diphtheria-causing  bacteria.  Horses  are  rendered  immune  by 
giving  them  the  diphtheria   toxin  in  gradually  increasing  doses. 


Antitoxin  for  diphtheria  prepared  by  the  New  York  Board  of  Health. 

The  serum  of  the  blood  of  these  horses  is  then  used  to  inoculate  the 
patient  suffering  from  or  exposed  to  diphtheria,  and  thus  the  dis- 
ease is  checked  or  prevented  altogether  by  the  antitoxin  injected 
into  the  blood.  The  laboratories  of  the  board  of  health  prepare 
this  antitoxin  and  supply  it  fresh  for  public  use. 

It  has  been  found  from  experience  in  hospitals  that  deaths  from 
diphtheria  are  largely  preventable  by  early  use  of  antitoxin. 
When  antitoxin  was  used  on  the  first  day  of  the  disease  no  deaths 
took  place.  If  not  used  until  the  second  day,  5  deaths  occurred 
in  every  hundred  cases,  on  the  third  day  11  deaths,  on  the  4th 
day  19  deaths,  and  on  the  5th  day  20  deaths  out  of  every  hun- 
dred cases.  It  is  therefore  advisable,  in  a  suspected  case  of 
diphtheria,  to  have  antitoxin  used  at  once  to  prevent  serious 
results. 

Vaccination.  —  Smallpox  was  once  the  most  feared  disease  in 
this  country ;  95  per  cent  of  all  people  suffered  from  it.     As  late 


392    MAN'S  IMPROVEMENT  OF  HIS   ENVIRONMENT 

as  1898,  over  50,000  persons  lost  their  lives  annually  in  Russia 
from  this  disease.  It  is  probably  not  caused  by  bacteria,  but  by 
a  tiny  animal  parasite.  Smallpox  has  been  brought  under  abso- 
lute control  by  vaccination,  —  the  inoculation  of  man  with  the 
substance  (called  virus)  which  causes  cowpox  in  a  cow.  Cowpox  is 
like  a  mild  form  of  smallpox,  and  the  introduction  of  this  virus 
gives  complete  immunity  to  smallpox  for  several  years  after  vac- 
cination. This  immunity  is  caused  by  the  formation  of  a  ger- 
micidal substance  in  the  blood,  due  to  the  introduction  of  the 
virus.  Another  function  of  the  board  of  health  is  the  prepara- 
tion and  distribution  of  vaccine  (material  containing  the  virus 
of  cowpox). 

Rabies  (Hydrophobia).  —  This  disease,  which  is  believed  to  be 
caused  by  a  protozoan  parasite,  is  communicated  from  one  dog  to 
another  in  the  saliva  by  biting.  In  a  similar  manner  it  is  trans- 
ferred to  man.  The  great  French  bacteriologist,  Louis  Pasteur, 
discovered  a  method  of  treating  this  disease  so  that  when  taken 
early  at  the  time  of  the  entry  of  the  germ  into  the  body  of  man, 
the  disease  can  be  prevented.  In  some  large  cities  (among  them 
New  York)  the  board  of  health  has  established  a  laboratory  where 
free  treatment  is  given  to  all  persons  bitten  by  dogs  suspected  of 
having  rabies. 

Vaccination  against  Typhoid.  —  Typhoid  fever  has  within  the 
past  five  years  received  a  new  check  from  vaccination  which  has 
been  introduced  into  our  army  and  which  is  being  used  with  good 
effect  by  the  health  departments  of  several  large  cities. 

The  following  figures  show  the  differences  between  number  of 
cases  and  mortality  in  the  army  in  1898  during  the  war  with  Spain 
and  in  1911  during  the  concentration  of  certain  of  our  troops  at 
San  Antonio,  Texas. 

1898  —  2nd    Division,   7th    Army  Corps,   Jacksonville,   Florida. 

June-October,  1898 

Mean  strength,  10,759. 

Cases  of  typhoid  certain  and  probable,  2693. 

Death  from  typhoid,  258. 

Death  from  all  diseases,  281. 


MAN'S   IMPROVEMENT  OF  HIS   ENVIRONMENT    393 

Manoeuver   Division,  San    Antonio,  Texas.     March  10-July  11, 

1911. 

Mean  strength,  12,801. 
Cases  of  typhoid,  1. 
Death  from  typhoid,  0. 
Deaths  all  diseases,  11. 

During  this  period  there  were  49  cases  of  typhoid  and  19  deaths 
in  the  near-by  city  of  San  Antonio.     But  in  camp,  where  vaccination 


Z  Ni3  Il,v.  7^At^my  Corp5 
Jacksonvi  lleTla.- June-Oct  I8S>3 


Nance  uvER  Div.-5an  Ah4TONio 
Texas.  Mah.io-JulvIi  ,1911. 


MEAN 
STRENGTH 


I0>759 


] 


ia.8oi 


CASES    OP 
TYPHOID 


TYPHOID 
DEATHS 


r 


DEATHS 
ALLDISEASES 


2693 

eei 


ONE 

NONE 
11 


Comparison  of  cases  of  and  death  from  typhoid  in  1898  and  1911.     What  have  we 

learned  about  combating  typhoid  since  1898  ? 

for  typhoid  was  required,  all  were  practically  immune.  In  the  army 
at  large,  since  typhoid  vaccination  has  been  practiced,  1908-1909, 
the  death  rate  from  typhoid  has  dropped  from  2.9  per  1000  to 
.03  per  1000,  a  wonderful  record  when  we  remember  that  during 
the  Spanish-American  War  86  per  cent  of  the  deaths  in  the  army 
were  from  typhoid  fever. 

How  the  Board  of  Health  fights  Tuberculosis.  —  Tuberculosis, 
which  a  few  years  ago  killed  fully  one  seventh  of  the  people  who 
died  from  disease  in  this  country,  now  kills  less  than  one  tenth. 
This  decrease  has  been  largely  brought  about  because  of  the  treat- 
ment of  the  disease.  Since  it  has  been  proved  that  tuberculosis  if 
taken  early  enough  is  curable,  by  quiet  living,  good  food,  and 
plenty  of  fresh  air  and  light,  we  find  that  numerous  sanitaria  have 
come  into  existence  which  are  supported  by  private  or  public 
means.  At  these  sanitaria  the  patients  live  out  of  doors,  especially 
sleep  in  the  air,  while  they  have  plenty  of  nourishing  food  and 
little  exercise.     The  department  of  health  of  New  York  City  main- 


394    MAN'S   IMPROVEMENT  OF   HIS   ENVIRONMENT 


tains  a  sanitarium  at  Otisville  in  the  Catskill  Mountains.     Here 
people  who  are  unable  to  provide  means  for  getting  away  from  the 


The    best   cures  for   tuberculosis   are   rest,  plenty  of   fresh   out-of-door  air,  and 

wholesome  food. 

city  are  cared  for  at  the  city's  expense  and  a  large  percentage  of 
them  are  cured.  In  this  way  and  by  tenement  house  laws  which 
require  proper  air  shafts  and  window  ventilation  in  dwellings,  by 
laws  against  spitting  in  public  places,  and  in  other  ways,  the  boards 
of  health  in  our  toTVTis  and  cities  are  waging  war  on  tuberculosis. 


A  sanitarium  for  tuberculosis.     Notice  the  outdoor  sleeping  rooms. 


MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT    395 

Ex-President  Roosevelt  said,  in  one  of  his  latest  messages  to 
Congress :  — 

"  There  are  about  3,000,000  people  seriously  ill  in  the  United 
States,  of  whom  500,000  are  consumptives.  More  than  half  of 
this  illness  is  preventable.  If  we  count  the  value  of  each  life  lost 
at  only  $1700  and  reckon  the  average  earning  lost  by  illness  at 
$700  a  year  for  grown  men,  we  find  that  the  economic  gain  from 
mitigation  of  preventable  disease  in  the  United  States  would  ex- 
ceed $1,500,000,000  a  year.  This  gain  can  be  had  through  medical 
investigation  and  practice,  school  and  factory  hygiene,  restriction 
of  labor  by  women  and  children,  the  education  of  the  people  in 
both  public  and  private  hygiene,  and  through  improving  the  effi- 
ciency of  our  health  service,  municipal,  state,  and  national." 

Work  of  the  Division  of  School  and  Infant  Hygiene.  —  Besides 
the  work  of  the  division  of  infectious  disease,  the  division  of  sani- 
tation, which  regulates  the  general  sanitary  conditions  of  houses 
and  their  surroundings  and  the  division  of  inspection,  which  looks 
after  the  purity  and  conditions  of  sale  and  delivery  of  milk  and 
foods,  there  is  another  department  which  most  vitally  concerns 
school  children.  This  is  the  division  of  school  and  infant  hygiene. 
The  work  of  this  department  is  that  of  the  care  of  the  children  of 
the  city.  During  the  year  1912,  279,776  visits  were  made  to  the 
homes  of  school  children  of  the  city  of  New  York  by  inspectors 
and  nurses.  Besides  this,  thousands  of  children  in  school  were 
cared  for  and  aided  by  the  city. 

Adenoids.  —  Many  children  suffer  needlessly  from  adenoids,  — 
growths  in  the  back  of  the  nose  or  mouth  which  prevent  sufficient 
oxygen  being  admitted  to  the  lungs.  A  child  suffering  from  these 
growths  is  known  as  a  ''  mouth  breather  "  because  the  mouth  is 
opened  in  order  to  get  more  air.  The  result  to  the  child  may  be  a 
handicap  of  deafness,  chronic  running  of  the  nose,  nervousness, 
and  lack  of  power  to  think.  His  body  cells  are  starving  for  oxygen. 
A  very  simple  operation  removes  this  growth.  Cooperation  on  the 
part  of  the  children  and  parents  with  the  doctors  or  nurses  of  the 
board  of  health  will  do  much  in  removing  this  handicap  from  many 
young  lives. 

Eyestrain.  —  Another  handicap  to  a  boy  or  girl  is  eyestrain. 


396    MAN'S  IMPROVEMENT  OF  HIS  ENVIRONMENT 

Twenty-two  per  cent  of  the  school  children  of  Massachusetts 
were  recently  found  to  have  defects  in  vision.  Tests  for  defective 
eyesight  may  be  made  at  school  easily  by  competent  doctors,  and 
if  the  child  or  parent  takes  the  advice  given  to  correct  this  by 
procuring  proper  glasses,  a  handicap  on  future  success  will  be 
removed. 

Decayed  Teeth.  —  Decayed  teeth  are  another  handicap,  cared 
for  by  this  division.  Free  dental  clinics  have  been  established  in 
many  cities,  and  if  children  will  do  their  share,  the  chances  of  their 
success  in  later  life  will  be  greatly  aided.  Boys  and  girls,  if  handi- 
capped with  poor  eyes  or  teeth,  do  not  have  a  fair  chance  in  life's 
competition.  In  a  certain  school  in  New  York  City  there  were 
236  pupils  marked  ''C"  in  their  school  work.  These  children 
were  examined,  and  126  were  found  to  have  bad  teeth,  54 
defective  vision,  and  56  other  defects,  as  poor  hearing,  adenoids, 
enlarged  tonsils,  etc.  Of  these  children  185  were  treated  for 
these  various  difficulties,  and  51  did  not  take  treatment.  During 
the  following  year's  work  176  of  these  pupils  improved  from  "  C  " 
to  "B"  or  ''A  ",  while  60  did  not  improve.  If  defects  are  such 
a  handicap  in  school,  then  what  would  be  the  chances  of  success 
in  life  outside. 

In  conclusion :  this  department  of  school  hygiene  deserves  the 
earnest  aid  of  every  young  citizen,  girl  or  boy.  If  each  of  us 
would  honestly  help  by  maintaining  quarantine  in  the  case  of 
contagious  disease,  by  observing  the  rules  of  the  health  depart- 
ment in  fumigation,  by  acting  upon  advice  given  in  case  of  eye- 
strain, bad  teeth,  or  adenoids,  and  most  of  all  by  observing  the 
rules  of  personal  hygiene  as  laid  down  in  this  book,  the  city  in 
which  we  live  would,  a  generation  hence,  contain  stronger,  more 
prosperous,  and  more  efficient  citizens  than  it  does  to-day. 

Reference  Books 

elementary 

Hunter,  Laboratory  Problems  in  Civic  Biology.     American  Book  Company. 
Davison,  The  Human  Body  and  Health.     American  Book  Company. 
Gulick  Hygiene  Series,  Town  and  City.     Ginn  and  Company. 
Hough  and  Sedgwick,   The  Human  Mechanism,  Part  II.     Ginn  and  Company. 
Overton,  General  Hygiene.     American  Book  Company. 


MAN^S  IMPROVEMENT  OF  HIS   ENVIRONMENT    397 

Richards,    Sanitation  in  Daily  Life.     Whitcomb  and  Barrows. 

Richmond  and  Wallach,  Good  Citizenship.     American  Book  Company. 

Ritchie,  Primer  of  Sanitation.     World  Book  Company. 

Sharpe,  Laboratory  Manual  of  Biology,  pages  320-334.    American  Book  Company. 

ADVANCED 

Allen,  Civics  and  Health.     Ginn  and  Company. 

Chapin,  Municipal  Sanitation  in  the  United  States.     Snow  and  Farnham. 

Chapin,  Sources  and  Modes  of  Infection.     Wiley  and  Sons. 

Conn,  Practical  Dairy  Bacteriology.     Orange  Judd  Company. 

Hough  and  Sedgwick,  The  Human  Mechanism.     Part  II.     Ginn  and  Company. 

Hutchinson,  Preventable  Diseases.     The  Houghton,  Mifflin  Company. 

Morse,  The  Collection  and  Disposal  of  Municipal  Waste.     Municipal  Journal  and 

Engineer. 
Overlock,  The  Working  People,  Their  Health  and  How  to  Protect  It.     Mass.  Health 

Book  Publishing  Co. 
Price,  Handbook  of  Sanitation.     Wiley  and  Sons. 
Tolman,  Hygiene  for  the  Worker.    American  Book  Company. 

REPORTS,    ETC. 

American  Health  Magazine. 

Annual  Report  of  Department  of  Health,  City  of  New  York  (and  other  cities). 

Bulletins  and  Publications  of  Committee  of  One  Hundred  on  National  Health. 

School  Hygiene,  American  School  Hygiene  Association. 

Grinnell,  Our  Army  versus  a  Bacillus.     National  Geographic  Magazine. 


XXV.     SOME  GREAT   NAMES   IN   BIOLOGY 

If  we  were  to  attempt  to  group  the  names  associated  with  the 
study  of  biology,  we  would  find  that  in  a  general  way  they  were 
connected  either  with  discoveries  of  a  purely  scientific  nature  or 
with  the  benefiting  of  man's  condition  by  the  application  of  the 
purely  scientific  discoveries.  The  first  group  are  necessary  in  a 
science  in  order  that  the  second  group  may  apply  their  work.  It 
was  necessary  for  men  like  Charles  Darwin  or  Gregor  Mendel  to 
prove  their  theories  before  men  like  Luther  Burbank  or  any  of 
the  men  now  working  in  the  Department  of  Agriculture  could 
benefit  mankind  by  growing  new  varieties  of  plants.  The  dis- 
covery of  scientific  truths  must  be  achieved  before  the  men  of 
modern  medicine  can  apply  these  great  truths  to  the  cure  or  pre- 
vention of  disease.  Since  we  are  most  interested  in  discoveries 
which  touch  directly  upon  human  life,  the  men  of  whom  this  chap- 
ter treats  will  be  those  who,  directly  or  indirectly,  have  benefited 
mankind. 

The  Discoverers  of  Living  Matter.  —  The  names  of  a  number  of 
men  living  at  different  periods  are  associated  with  our  first  knowl- 
edge of  cells.  About  the  middle  of  the  seventeenth  century  micro- 
scopes came  into  use.  Through  their  use  plant  cells  were  first 
described  and  pictured  as  hollow  boxes  or  "  cells."  But  it  was 
not  until  1838  that  two  German  friends,  Schleiden  and  Schwann 
by  name,  working  on  plants  and  animals,  discovered  that  both  of 
these  forms  of  life  contained  a  jellylike  substance  that  later  came 
to  be  called  protoplasm.  Another  German  named  Max  Schultz  in 
1861  gave  the  name  protoplasm  to  all  living  matter,  and  a  little  later 
still  Professor  Huxley,  a  famous  Englishman,  friend  and  champion 
of  Charles  Darwin,  called  attention  to  the  physical  and  chemical 
qualities  of  protoplasm  so  that  it  came  to  be  known  as  the  chemical 
and  physical  basis  of  life. 

398 


SOME   GREAT  NAMES   IN   BIOLOGY 


399 


Life  comes  from  Life.  —  Another  group  of  men,  after  years  of 
patient  experimentation,  worked  out  the  fact  that  life  comes  from 
other  life.  In  ancient  times  it 
was  thought  that  Hfe  arose 
spontaneously ;  for  example, 
that  fish  or  frogs  arose  out  of 
the  mud  of  the  river  bottoms, 
and  that  insects  came  from  the 
dew  or  rotting  meat.  It  was 
beUeved  that  bacteria  arose 
spontaneously  in  water,  even 
as  late  as  1876,  when  Professor 
Tyndall  proved  by  experiment 
the  contrary  to  be  true. 

As  early  as  1651  William 
Harvey,  the  court  physician  of 
Charles  I  of  England,  showed 
that  all  life  came  from  the  egg. 
It  was  much  later,  however, 
that  the  part  played  by  the 
sperm  and  egg  cell  in  fertiliza- 
tion was  carefully  worked  out. 
It  is  to  Harvey,  too,  that  we 
owe  the  beginnings  of  our 
knowledge  of  the  circulation 
of  the  blood.  He  showed  that 
blood  moved  through  tubes  in  the  body  and  that  the  heart  pumped 
it.  He  might  be  called  the  father  of  modern  physiology  as  well 
as  the  father  of  embryology.  A  long  list  of  names  might  be  added 
to  that  of  Harvey  to  show  how  gradually  our  knowledge  of  the 
working  of  the  human  body  has  been  added  to.  At  the  present 
time  we  are  far  from  knowing  all  the  functions  of  the  various  parts 
of  the  human  engine,  as  is  shown  by  the  number  of  investigators 
in  physiology  at  the  present  time.  Present-day  problems  have 
much  to  do  with  the  care  of  the  human  mechanism  and  with  its 
surroundings.  The  solution  of  these  problems  will  come  from  ap- 
plying the  sciences  of  hygiene,  preventive  medicine,  and  sanitation. 


Prof.  Tyndall's  experiment  to  show  that  if 
air  containing  germs  is  kept  from  or- 
ganic substances,  such  substances  will 
not  decay.  The  box  is  sterilized;  like- 
wise the  tubes  (t)  containing  nutrients. 
Air  is  allowed  to  enter  by  the  tubes  (w), 
which  are  so  made  that  dust  is  pre- 
vented from  entering.  A  thermometer 
{th)  records  the  temperature.  The  sub- 
stances in  the  tubes  do  not  decay,  no 
matter  how  favorable  the  temperature. 


400 


SOME  GREAT   NAMES   IN   BIOLOGY 


In  the  preceding  chapters  of  this  book  we  have  learned  some- 
thing about  our  bodies  and  their  care.  We  have  found  that  man 
is  able  within  limitations  to  control  his  environment  so  as  to  make 
it  better  to  live  in.  All  of  the  scientific  facts  that  have  been  of 
use  to  man  in  the  control  of  disease  have  been  found  out  by  men 
who  have  devoted  their  lives  in  the  hope  that  their  experiments 
and  their  sacrifices  of  time,  energy,  and  sometimes  life  itself  might 
make  for  the  betterment  of  the  human  race.  Such  men  were 
Harvey,  Jenner,  Lister,  Koch,  and  Pasteur. 

Edward  Jenner  and  Vaccination.  —  The  civilized  world  owes 
much  to  Edward  Jenner,  the  discoverer  of  vaccination  against 
smallpox.  Born  in  Berkeley,  a  little  town  of  Gloucestershire,  Eng- 
land, in  1749,  as  a  boy  he 
showed  a  strong  liking  for  nat- 
ural history.  He  studied  medi- 
cine and  also  gave  much  time  to 
the  working  out  of  biological 
problems.  As  early  as  1775  he 
began  to  associate  the  disease 
called  cowpox  with  that  of 
smallpox,  and  gradually  the 
idea  of  inoculation  against  this 
terrible  scourge,  which  killed  or 
disfigured  hundreds  of  thou- 
sands every  year  in  England 
alone,  was  worked  out  and  ap- 
plied. He  believed  that  if  the 
two  diseases  were  similar,  a  per- 
son inoculated  with  the  mild 
disease  (cowpox)  would  after  a 
slight  attack  of  this  disease  be 
immune  against  the  more  deadly  and  loathsome  smallpox.  It  was 
not  until  1796  that  he  was  able  to  prove  his  theory,  as  at  first  few 
people  would  submit  to  vaccination.  War  at  this  time  was  being 
waged  between  France  and  England,  so  that  the  former  country, 
usually  so  quick  to  appreciate  the  value  of  scientific  discoveries,  was 
slow  to  give  this  method  a  trial.     In  spite  of  much  opposition,  how- 


Edward   Jenner,  the    discoverer   of    vac- 
cination. 


SOME  GREAT  NAMES   IN   BIOLOGY 


401 


ever,  by  the  year  1802,  vaccination  was  practiced  in  most  of  the 
civilized  countries  of  the  world.  At  the  present  time  the  death  rate 
in  Great  Britain,  the  home  of  vaccination,  is  less  than  .3  to  every 
1,000,000  living  persons.  This  shows  that  the  disease  is  practically 
wiped  out  in  England.  An  interesting  comparison  with  these 
figures  might  be  made  from  the  history  of  the  disease  in  parts  of 
Russia  where  vaccination  is  not  practiced.  There,  thousands  of 
deaths  from  smallpox  occur  annually.  During  the  winter  of 
1913-1914  an  epidemic  of  smallpox  with  more  than  250  cases 
broke  out  in  the  city  of  Niagara  Falls.  This  epidemic  appears 
to  be  due  to  a  campaign  conducted  by  people  who  do  not  believe 
in  vaccination.  In  cities  and  towns  near  by,  where  vaccination 
was  practiced,  no  cases  of  smallpox  occurred.  Naturally  if  oppo- 
sition to  vaccination  is  found  nowadays,  Jenner  had  a  much 
harder  battle  to  fight  in  his  day.  He  also  had  many  failures,  due 
to  the  imperfect  methods  of  his  time.  The  full  worth  of  his  dis- 
covery was  not  fully  appreciated  until  long  after  his  death,  which 
occurred  in  1823. 

Louis  Pasteur.  —  The  one  man  who,  in  biological  science,  did 
more  than  any  other  to  directly  benefit  mankind  was  Louis  Pasteur. 
Born  in  1822,  in  the  mountains 
near  the  border  of  northeastern 
France,  he  spent  the  early  part 
of  his  life  as  a  normal  boy,  fond 
of  fishing  and  not  very  partial 
to  study.  He  inherited  from 
his  father,  however,  a  fine  char- 
acter and  grim  determination, 
so  that  when  he  became  inter- 
ested in  scientific  pursuits  he 
settled  down  to  work  with  en- 
thusiasm and  energy. 

At  the  age  of  twenty-five  he 
became  well  known  throughout 
France  as  a  physicist.     Shortly 
after  this  he  became  interested  in  the  tiny  plants  we  call  bac- 
teria, and  it  was  in  the  field  of  bacteriology  that  he  became  most 

HUNTER,    CIV.    BI. 26 


Louis  Pasteur. 


(102  SOME  GREAT  NAMES  IN  BIOLOGY 

famous.  First  as  professor  at  Strassburg  and  at  Lille,  later  as 
director  of  scientific  studies  in  the  Ecole  Normale  at  Paris,  he 
showed  his  interest  in  the  application  of  his  discoveries  to  human 
welfare. 

i  In  1857  Pasteur  showed  that  fermentation  was  due  to  the  pres- 
ence of  bacteria,  it  having  been  thought  up  to  this  time  that  it 
was  a  purely  chemical  process.  This  discovery  led  to  very 
practical  ends,  for  France  was  a  great  wine-producing  country, 
and  with  a  knowledge  of  the  cause  of  fermentation  many  of  the 
diseases  which  spoiled  wine  were  checked. 

In  1865-1868  Pasteur  turned  his  attention  to  a  silkworm  dis- 
ease which  threatened  to  wipe  out  the  silk  industry  of  France  and 
Italy.  He  found  that  this  disease  was  caused  by  bacteria.  After 
a  careful  study  of  the  case  he  made  certain  recommendations 
which,  when  carried  out,  resulted  in  the  complete  overthrow  of  the 
disease  and  the  saving  of  millions  of  dollars  to  the  poor  people  of 
France  and  Italy. 

The  greatest  service  to  mankind  came  later  in  his  life  when  he 
applied  certain  of  his  discoveries  to  the  treatment  of  disease. 
First  experimenting  upon  chickens  and  later  with  cattle,  he  proved 
that  by  making  a  virus  (poison)  from  the  germs  which  caused 
certain  diseases  he  could  reduce  this  virus  to  any  desired  strength. 
He  then  inoculated  the  animals  with  the  virus  of  reduced  strength, 
giving  the  inoculated  animals  a  mild  attack  of  the  disease,  and 
found  that  this  made  them  immune  from  future  attacks.  This 
discovery,  first  applied  to  chicken  cholera,  laid  the  foundation  for 
all  future  work  in  the  uses  of  serums,  vaccines,  and  antitoxins. 

Pasteur  was  perhaps  the  best  known  through  his  study  of 
rabies.  The  great  Pasteur  Institute,  founded  by  popular  sub- 
scriptions from  all  over  the  world,  has  successfully  treated  over 
22,000  cases  of  rabies  with  a  death  rate  of  less  than  1  per  cent. 
But  more  than  that  it  has  been  the  place  where  Roux,  a  fellow 
worker  with  Pasteur,  discovered  the  antitoxin  for  diphtheria  which 
has  resulted  in  the  saving  of  thousands  of  human  lives.  Here 
also  have  been  established  the  principles  of  inoculation  against 
bubonic  plague,  lockjaw,  and  other  germ  diseases. 

Pasteur  died  in  1895  at  the  age  of  seventy-three,  "  the  most 


SOME  GREAT  NAMES   IN  BIOLOGY 


403 


perfect  man  in  the  realm  of  science,"  a  man  beloved  by  his  coun- 
trymen and  honored  by  the  entire  world. 

Robert  Koch.  —  Another  name  associated  with  the  battle 
against  disease  germs  is  that  of  Robert  Koch.  Born  in  Klausthal, 
Hanover,  in  1843,  he  later  be- 
came a  practicing  physician, 
and  about  1880  was  called  to 
Berlin  to  become  a  member  of 
the  sanitary  commission  and 
professor  in  the  school  of  medi- 
cine. In  1881  he  discovered 
the  germ  that  causes  tubercu- 
losis and  two  years  later  the 
germ  that  causes  Asiatic  chol- 
era. His  later  work  has  been 
directed  toward  the  discovery 
of  a  cure  for  tuberculosis  and 
other  germ  diseases.  As  yet, 
however,  no  certain  cure  seems 
to  have  been  found. 

Lister  and  Antiseptic  Treat- 
ment of  Wounds.  —  A  third 
great  benefactor  of  mankind 
was  Sir  Joseph  Lister,  an  Eng- 
lishman who  was  born  in  1827. 

As  a  professor  of  surgery  he  first  applied  antiseptics  in  the  op- 
erating room.  By  means  of  the  use  of  carbolic  acid  or  other 
antiseptics  on  the  surface  of  wounds,  on  instruments,  and  on 
the  hands  and  clothing  of  the  operating  surgeons,  disease  germs 
were  prevented  from  taking  a  foothold  in  the  wounds.  Thus 
blood  poisoning  was  prevented.  This  single  discovery  has  done 
more  to  prevent  death  after  operations  than  any  other  of  recent 
time. 

Modern  Workers  on  the  Blood.  —  At  the  present  time  several 
names  stand  out  among  investigators  on  the  blood.  Paul  Ehrlich, 
a  German  born  in  1854,  is  justly  famous  for  his  work  on  the  blood 
and  its  relation  to  immunity   from  certain  diseases.     His  able 


Robert  Koch. 


404 


SOME   GREAT  NAMES   IN  BIOLOGY 


research  work  has  given  the  world  a  much  better  understanding  of 
the  problem  of  acquired  immunity. 

Another  name  associated  with  the  blood  is  that  of  Elias  Metch- 
nikoff,  a  Russian.  He  was  born  in  1845.  Metchnikoff  first 
advanced  the  belief  that  the  colorless  blood  corpuscles,  or  phagocytes, 
did  service  as  the  sanitary  police  of  the  body.  He  has  found  that 
there  are  several  different  kinds  of  colorless  corpuscles,  each  having 
somewhat  different  work  to  do.  Much  of  the  modern  work  done 
by  physiologists  on  the  blood  are  directly  founded  on  the  dis- 
coveries of  Metchnikoff. 

Heredity  and  Evolution.  Charles  Darwin.  —  There  is  still  an- 
other important  line  of  investigation  in  biology  that  we  have  not 
mentioned.  This  is  the  doctrine  of  evolution  and  the  allied  dis- 
coveries along  the  line  of  heredity.  The  development  or  evolution 
of  plants  and  animals  from  simpler  forms  to  the  many  and  present 
complex  forms  of  life  have  a  practical  bearing  on  the  betterment 

of  plants  and  animals,  in- 
cluding man  himself.  The 
one  name  indelibly  associ- 
ated with  the  word  evolu- 
tion is  that  of  Charles 
Darwin. 

Charles  Darwin  was  born 
on  February  12,  1809,  a  son 
of  well-to-do  parents,  in  the 
pretty  English  village  of 
Shrewsbury.  As  a  boy  he 
was  verv  fond  of  out-of- 
door  life,  was  a  collector  of 
birds'  eggs,  stamps,  coins, 
shells,  and  minerals.  He 
was  an  ardent  fisherman, 
and  as  a  young  man  be- 
came an  expert  shot.  His  studies,  those  of  the  English  classical 
school,  were  not  altogether  to  his  liking.  It  is  not  strange,  per- 
haps, that  he  was  thought  a  very  ordinary  boy,  because  his  in- 
terest in  the  out-of-doors  led  him  to  neglect  his  studies.     Later  he 


Charles  Darwin,  the  grand  old  man  of  biology. 


SOME  GREAT  NAMES  IN  BIOLOGY  405 

was  sent  to  Edinburgh  University  to  study  medicine.  Here  the 
dull  lectures,  coupled  with  his  intense  dislike  for  operations,  made 
him  determine  never  to  become  a  physician.  But  all  this  time  he 
showed  his  intense  interest  in  natural  history  and  took  frequent 
part  in  the  discussions  at  the  meetings  of  one  of  the  student  zo- 
ological societies. 

In  1828  his  father  sent  him  to  Cambridge  to  study  for  the 
ministry.  His  three  years  at  the  university  were  wasted  so  far 
as  preparation  for  the  ministry  were  concerned,  but  they  were  in- 
valuable in  shaping  his  future.  He  made  the  acquaintance  of  one 
or  two  professors  who  were  naturalists  like  himself,  and  in  their 
company  he  spent  many  happy  hours  in  roaming  over  the  coun- 
tryside collecting  beetles  and  other  insects.  In  1831  an  event 
occurred  which  changed  his  career  and  made  Darwin  one  of  the 
world's  greatest  naturalists.  He  received  word  through  one  of 
his  professional  friends  that  the  position  of  naturalist  on  her 
Majesty's  ship  Beagle  was  open  for  a  trip  around  the  world.  Dar- 
win applied  for  the  position,  was  accepted,  and  shortly  after  started 
on  an  eventful  five  years'  trip  around  the  world.  He  returned  to 
England  a  famous  naturalist  and  spent  the  remainder  of  his  long 
and  busy  life  producing  books  which  have  done  more  than  those 
of  any  other  writer  to  account  in  a  satisfactory  Way  for  the  changes 
of  form  and  habits  of  plants  and  animals  on  the  earth.  His 
theories  established  a  foundation  upon  which  plant  and  animal 
breeders  were  able  to  work. 

His  wonderful  discovery  of  the  doctrine  of  evolution  was  due 
not  only  to  his  information  and  experimental  evidence,  but  also 
to  an  iron  determination  and  undaunted  energy.  In  spite  of 
almost  constant  illness  brought  about  by  eyestrain,  he  accom- 
plished more  than  most  well  men  have  done.  His  life  should 
mean  to  us  not  so  much  the  association  of  his  name  with  the 
Origin  of  Species  or  Plants  and  Animals  under  Domestication, 
two  of  his  most  famous  books,  but  rather  that  of  a  patient, 
courteous,  and  brave  gentleman  who  struggled  with  true  English 
pluck  against  the  odds  of  disease  and  the  attacks  of  hostile  critics. 
He  gave  to  the  world  the  proofs  of  the  theory  on  which  we  to-day 
base  the  progress  of  the  world.     DarWin  lived  long  enough  to  see 


406  SOME   GREAT  NAMES   IN   BIOLOGY 

many  of  his  critics  turn  about  and  come  over  to  his  beliefs.  He 
died  on  the  19th  of  April,  1882,  at  seventy-four  years  of  age. 

Associated  with  Darwin's  name  we  must  place  two  other  cO' 
workers  on  heredity  and  evolution,  Alfred  Russel  Wallace,  an 
Englishman  who  independently  and  at  about  -the  same  time 
reached  many  of  the  conclusions  that  Darwin  came  to,  and  August 
Weissman,  a  German.  The  latter  showed  that  the  protoplasm  of 
the  germ  cells  (eggs  and  sperms)  is  directly  handed  down  from 
generation  to  generation,  they  being  different  from  the  other  body 
cells  from  the  very  beginning.  In  1883  a  German  named  Boveri 
discovered  that  the  chromosomes  of  the  egg  and  the  sperm  cell 
were  at  the  time  of  fertilization  just  half  in  number  of  the  other 
cells  (see  page  252)  so  that  a  fertilized  egg  was  really  a  whole  cell 
made  up  of  tivo  half  cells,  one  from  each  parent.  The  chromosomes 
within  the  nucleus,  we  remember,  are  beheved  to  be  the  bearers 
of  the  hereditary  qualities  handed  down  from  parent  to  child. 
This  discovery  shows  us  some  of  the  mechanics  of  heredity. 

Applications  to  Plant  and  Animal  Breeding.  —  Turning  to  the 
practical  applications  of  the  scientific  work  on  the  method  of 
heredity,  the  name  of  Gregor  Mendel,  an  Austrian  monk,  stands 
out  most  prominently.  Mendel  lived  from  1822  until  1884.  His 
work,  of  which  we  already  have  learned  something  (see  page  258), 
remained  undiscovered  until  a  few  years  ago.  The  application  of 
his  methods  to  plant  and  animal  raising  are  of  the  utmost  impor- 
tance because  the  breeder  is  able  to  separate  the  qualities  he  desires 
and  breed  for  those  qualities  only.  Another  name  we  have  men- 
tioned with  reference  to  plant  breeding  is  Hugo  de  Vries,  the 
Dutchman  who  recently  showed  that  in  some  cases  plants  arise 
as  new  species  by  sudden  and  great  variations  known  as  mutations. 
And  lastly,  in  our  own  California,  Luther  Burbank,  by  careful 
hybridizing,  is  making  lasting  fame  with  his  new  and  useful  hybrid 
plants. 

References 

Conn,  Biology.    Silver,  Burdett  &  Co. 

Darwin,  Life  and  Letters  of  Charles  Darwin.    Appletons. 

Galton,  Hereditary  Genius.     London  (1892). 

Thompson,  Heredity.     John  Murray,  London  England. 

Wasmann,  Problem  of  Evolution.  Kegan  Paul,  Trench,  Triibner  and  Co.,  London,  E.  C. 


APPENDIX 

A  SUGGESTED  OUTLINE    FOR    BIOLOGY  BEGINNING 

IN   THE  FALL 

LIST  OF  TOPICS 

First  Term 

First  week.  Why  study  Biology?  Relation  to  human  health,  hygiene.  Rela- 
tions existing  between  plants  and  animals.  Relation  of  bacteria  to  man. 
Uses  of  plants  and  animals.  Conservation  of  plants  and  animals.  Relation 
to  life  of  citizen  in  the  city.  Plants  and  animals  in  relation  to  their  environ- 
ment. What  is  the  environment;  light,  heat,  water,  soil,  food,  etc.  What 
plants  take  out  of  the  environment.  What  animals  take  out  of  the  environ- 
ment. Dependence  of  plants  and  animals  upon  the  factors  of  the  environ- 
ment. Laboratory:  Study  of  a  plant  or  an  animal  in  the  school  or  at 
home  to  determine  what  it  takes  from  its  environment. 

Second  week.  Some  Relations  existing  between  Plants  (Green)  and 
Animals.  Field  trip  planned  to  show  that  insects  feed  upon  plants ;  make 
their  homes  upon  plants.  That  flowers  are  pollinated  by  insects.  Insects 
lay  eggs  upon  certain  food  plants.  Green  plants  make  food  for  animals. 
Other  relations.  (Time  allotment.  One  day  trip,  collecting,  etc. ;  two  days' 
discussion  of  trip  in  all  its  relations.)  Make  a  careful  study  of  the  locality 
you  wish  to  visit,  have  a  plan  that  the  pupUs  know  about  beforehand. 
Review  and  hygiene  of  pupil's  environment,  2  days. 

Third  week.  Study  of  a  Flower,  Parts  Essential  to  Pollination  Named. 
Adaptations  for  insect  pollination  worked  out  in  laboratory.  Study  of 
bee  or  butterfly  as  an  insect  carrier  of  pollen.  Names  of  parts  of  insect 
learned.  Elementary  knowledge  of  groups  of  insects  seen  on  field  trip. 
Bees,  butterflies,  grasshoppers,  beetles,  possibly  flies  and  bugs.  Drawing 
of  a  flower,  parts  labeled.  Drawing  of  an  insect,  outline  only,  parts  labeled. 
Careful  study  of  some  fall  flower  fitted  for  insect  pollination  with  an  insect 
as  pollinating  agent.  Some  examples  of  cross-pollination  explained.  Prac- 
tical value  of  cross-pollination. 

Fourth  week.  Living  Plants  and  Animals  Compared.  Parts  of  plants,  func- 
tions ;  organs,  tissues,  cells.  Demonstration  cells  of  onion  or  elodea.  How 
cells  form  others.  What  living  matter  can  do.  Reproduction.  Growth  of 
pollen  tube,  fertilization.  Development  of  o\aile  into  seed.  Fruits,  how 
formed.     Uses,  to  man. 

Fifth  week.  What  makes  a  Seed  Grow.  Bean  seed,  a  baby  plant,  and  food 
supply.  Food,  what  is  it?  Organic  nutrients,  tests  for  starch,  protein,  oil. 
Show  their  presence  in  seeds. 

407 


408  APPENDIX 

Sixth  week.  Need  for  Foods.  Germination  of  bean  due  to  (a)  presence  o! 
foods,  (b)  outside  factors.  What  is  done  with  the  food.  Release  of  energy. 
Examples  of  engine,  plants,  human  body.  Oxidation  in  body.  Proof  by 
experiment.  Test  for  presence  of  CO2.  Oxidation  in  growing  plant,  experi- 
ment.    Respiration  a  general  need  for  both  plants  and  animals. 

Seventh  week.  Need  for  Digestion.  The  com  grain.  Parts,  growth,  food 
supply  outside  body  of  plant,  how  does  it  get  inside.  Digestion,  need  for. 
Tost  for  grape  sugar.    Enzymes,  their  function.    Action  of  diastase  on  starch. 

Eighth  week.  What  Plants  take  from  the  Soil,  How  they  do  This.  Use  of 
root.  Influence  of  gravity  and  water.  Why?  Absorption  a  function. 
Root  hairs.  Demonstration.  Pocket  gardens,  optional  home  work,  but  each 
pupil  must  work  on  root  hairs  from  actual  specimen.  How  root  absorbs. 
Osmosis ;  what  substances  will  osmose.     Experiments  to  demonstrate  this. 

Ninth  week.  Composition  of  Soil.  What  root  hairs  take  out  of  soU.  Plant 
needs  mineral  matter  to  make  living  matter.  Why?  Nitrogen  necessary. 
Sources  of  nitrogen,  the  nitrogen-fixing  bacteria.  Relation  of  this  to  man. 
Rotation  of  crops. 

Tenth  week.  How  Green  Plants  make  Food.  Passage  of  liquids  up  stem. 
Demonstration.  Structure  of  a  green  leaf.  Cellular  structure  demonstrated. 
Microscopic  demonstration  of  cells,  stoma,  air  spaces,  chlorophyll  bodies. 
Evaporation  of  water  from  green  leaf,  regulation  of  transpiration. 

Eleventh  week.  Midterm  Examinations.  Sun  a  source  of  energy.  Effect  of 
light  on  green  plants.  Experimental  proof.  Starch  made  in  green  leaf. 
Light  and  air  necessary  for  starch  making.  Proof.  Protein  making  in 
leaf.     By-products  in  starch  making.     Proof.     Respiration. 

Twelfth  week.  The  Circulation  and  Distribution  of  Food  in  Green  Plants. 
Uses  of  bark,  wood,  what  part  of  stem  does  food  pass  down.  Willow  twig 
experiment.  Summary  of  functions  of  living  matter  in  plant.  Forestry 
lecture.     Economic  uses  of  green  plants.    Reports. 

Thirteenth  week.  Plants  without  Chlorophyll  in  their  Relation  to  Man. 
Saprophytic  fungi.  Molds.  Growth  on  bread  or  other  substances.  Con- 
ditions most  favorable  for  growth.  Favorite  foods.  Methods  of  pre- 
vention.    Economic  importance. 

Fourteenth  week.  Yeasts  in  their  Relation  to  Man.  Experiments  to  show 
fermentation  is  caused  by  yeasts.  Experiments  to  show  conditions 
necessary  for  fermentation.  The  part  played  by  yeasts  in  bread  making, 
in  wine  making,  in  other  industries.  Structure  of  yeast  demonstrated. 
Summary. 

Fifteenth  week.  Experiments  to  show  where  Bacteria  may  be  found  and 
Conditions  necessary  to  Growth  Begun.  Have  cultures  collected 
and  placed  in  a  warm  room  during  the  holidays.  Suggested  experiments 
are  exposure  to  air  of  quiet  room  and  room  with  persons  moving,  dust  of 
floor,  knife  blade,  etc. 

Sixteenth,  seventeenth,  and  eighteenth  weeks.  The  Month  of  January  should 
be  devoted  to  the  Study  of  Bacteria  in  their  General  Relations 
TO  Man.  Economically,  both  directly  and  indirectly.  Especial  emphasis 
placed  on  the  nature  and  necessity  of  decay.  Bacteria  in  relation  to  disease 
should  also  be  emphasized.  The  experiments  to  be  performed  and  the 
topics  expected  to  be  covered  follow. 


i 


APPENDIX  409 

Conditions  Favorable  and  Unfavorable  for  Growth  of  Bacteria.  (Use 
bouillon  cultures.)  Effect  of  intense  heat,  sterile  bouillon  exposed  to  air, 
effect  of  boiling,  effect  of  cold,  effect  of  antiseptics  (corrosive  sublimate, 
carbolic  acid,  boric  acid,  formalin,  etc.),  effect  of  large  amounts  of  sugar  and 
salt  and  the  relation  of  this  to  preserving,  etc.  Bring  out  practical  appli- 
cation of  principles  demonstrated.  Discuss  sterilization  in  medicine  and 
surgery,  cold  storage,  canning,  sterilization,  e.g.  laundries,  etc.,  use  of  anti- 
septics, preserving  by  means  of  salt  and  sugar.  Microscopic  demonstration 
of  bacteria.  Methods  of  reproduction.  Importance  in  causing  organic 
decay,  fixation  of  nitrogen,  various  useful  forms  in  cheese  making,  butter 
ripening,  etc.  Harmfulness  of  bacteria  as  disease  producers.  Specific  dis- 
eases discussed :  tuberculosis,  typhoid,  infective  colds,  blood  poisoning, 
etc.  Vaccination.  Antitoxins  begun  —  continued  after  knowledge  of 
human  body  is  gained.  Work  of  Lister  and  Pasteur. 
Nineteenth  and  twentieth  weeks.     Review  and  Examinations. 


Second  Term 

First  week.  The  Balanced  Aquarium.  Carbon  and  nitrogen  cycles.  Balanced 
aquarium  and  hay  infusion  compared. 

Second  week.  One  Protozoan,  Demonstration  to  show  Changes  in  Shape, 
Response  to  Stimuli,  Summary  of  Vital  Processes  in  Cell.  Food 
getting,  digestion,  assimilation,  oxidation,  excretion,  growth,  reproduction. 
Internal  structure  of  protozoan.     Protozoa  as  cause  of  disease. 

Third  week.  General  Survey  of  Animal  Kingdom.  Survey  introduced  by 
museum  trip  if  possible.  Protozoa,  worm,  insect,  fish,  mammal.  Distinc- 
tion between  vertebrate  and  invertebrate.  Character  of  mammalia.  Divi- 
sion of  labor  emphasized.     Man's  place  in  nature. 

Fourth  week.  Study  of  the  Frog.  Relation  to  habitat,  adaptations  for  loco- 
motion, food  getting,  respiration,  comparison  of  frog  and  fish  on  latter  point. 
Osmotic  exchange  of  gases  emphasized.     Cell  respiration. 

Fifth  week.  Metamorphosis  of  Frog.  Fertilization,  cell  division,  and  differ- 
entiation emphasized.  Touch  on  plant  and  animal  breeding.  Function 
of  chromosomes  as  bearers  of  heredity.  Comparison  of  bird's  egg  and  mam- 
mal embryo. 

Sixth  week.  Factors  in  Breeding.  1.  Variation.  2.  Selection.  3.  Heredity  fixes 
variation.  4.  Hybridizing.  5.  Control  of  environment.  Eugenics  in  relation 
to  (a)  crime,  (6)  disease,  (c)  genius.  Continuity  of  germ  plasm.  Work  of 
Darwin,  Mendel,  De  Vries,  Burbank. 

Seventh  week.  A  Brief  Study  of  the  Gross  Structure  of  the  Human  Body. 
Skin,  muscles,  bones.  Removal  of  lime  from  bone  by  HCl  to  show  other 
substances  and  need  for  lime.  Effect  of  posture,  spinal  curvature,  fractures, 
sprains. 

Eighth  week.  Need  for  Food.  Nutritive  value  of  food.  Use  of  charts  to  show 
foods  rich  in  carbohydrates,  fats,  proteins,  minerals,  water,  refuse.  The 
relation  of  age,  sex,  work,  and  environment  to  the  food  requirements.  What 
is  a  cheap  food.  Price  list  of  common  foods  at  present  time.  Efforts  of 
government  to  secure  a  cheap  food  supply  for  the  people.  Digestibility  of 
foods. 


410  APPENDIX 

Ninth  week.  How  the  Fuel  Value  of  Food  has  been  Determined.  Meaning 
of  calorie.  The  100-caloric  portion,  its  use  in  determining  a  daily  or  weekly 
dietary.  Standard  dietary  as  determined  by  Atwater.  Comparison  of 
standards  of  Chittenden  and  Voit  with  those  of  Atwater. 

Tenth  week.  Study  of  Pupil's  Dietary.  Planning  ideal  meals.  Individual 
dietaries  for  one  day  required  from  each  pupil.  Discussions  and  corrections. 
The  family  dietary.    Relation  to  cost. 

Eleventh  week.  Digestion.  The  digestive  system  in  the  frog  and  in  man  com- 
pared. Drawings  of  each.  Glands  and  enzymes.  Internal  secretions  and 
their  importance.  Demonstration  of  glandular  tissues.  Experiment  to 
show  digestion  of  starch  in  mouth. 

Twelfth  week.  Digestion  Continued.  Digestion  of  white  of  egg  by  gastric 
juice.  Digestion  of  starch  with  pancreatic  fluid.  Functions  of  pancreatic 
juice.  Microscopic  examination  of  emulsion.  Reasons  for  digestion. 
Part  played  by  osmosis.  Demonstration  of  osmosis.  Non-osmosis  of  non- 
digested  foods,  comparison  between  osmosable  qualities  of  starch  and  grape 
sugar. 

Thirteenth  week.  Absorption.  Where  and  how  foods  are  absorbed.  The 
structure  of  a  villus  explained.  Course  taken  by  foods  after  absorption. 
Function  of  liver.  Blood  making  the  result  of  absorption.  Composition  of 
blood,  red  and  colorless  corpuscles,  plasma,  blood  plates,  antibodies. 
Microscopic  drawing  of  corpuscles  of  frog's  and  man's  blood. 

Fourteenth  week.  Circulation  of  Blood.  The  heart  and  lungs  of  frog  demon- 
strated. Heart  of  man  a  force  pump,  explain  with  use  of  force  pump. 
Demonstration  of  beef's  heart.  Circulation  and  changes  of  blood  in  various 
parts  of  body.  Work  of  cells  with  reference  to  blood  made  clear.  Capillary 
circulation  (demonstration  of  circulation  in  tadpole's  tail  or  web  of  frog's 
foot). 

Fifteenth  week.  Respiration  and  Excretion.  Necessity  for  taking  of  oxygen 
to  cells  and  removal  of  wastes  from  cells.  Part  played  by  blood  and  lymph. 
Mechanics  of  breathing  (use  of  experiments).  Changes  of  air  and  blood  in 
lungs  (experiments).  Best  methods  of  ventilation  (experiments).  Elimi- 
nation of  wastes  from  blood  by  lungs,  skin,  and  kidneys.     Cell  respiration. 

Sixteenth  week.  Hygiene  of  Organs  of  Excretion,  especially  care  of  skin.  The 
general  structure  and  functions  of  the  central  nervous  system.  Sensory 
and  motor  nerves.  Reflexes,  instincts,  habits.  Habit  formation,  importance 
of  right  habits.  Rules  for  habit  formation.  Habit-forming  drugs  and  other 
agents.     Lecture. 

Seventeenth,  eighteenth,  nineteenth  weeks.  Civic  Hygiene  and  Sanitation. 
Hygiene  of  special  senses,  eye  and  ear.  A  well  citizen  an  efficient  citizen. 
Public  health  is  purchasable.  Improvement  of  environment  a  means  of 
obtaining  this.  Civic  hygiene  and  sanitation.  Cleaning  up  neighborhood, 
inquiry  into  home  and  street  conditions.  Fighting  the  fly.  Conditions  of 
milk  and  water  supply.  Relation  of  above  to  disease.  Work  of  Board  of 
Health,  etc.     Review  and  Examinations. 


APPENDIX  411 

SUGGESTED   SYLLABUS  FOR  COURSE   BEGINNING    FEB- 
RUARY  1  AND   ENDING   THE   FOLLOWING  JANUARY 

First  Term 

First  week.  Why  study  Biology?  Relation  to  human  health,  hygiene.  Rela- 
tions existing  between  plants  and  animals.  Relation  of  bacteria  to  man. 
Uses  of  plants  and  animals.  Conservation  of  plants  and  animals.  Relation 
to  life  of  citizen  in  this  city.  Needs  of  plants  and  animals  :  (1)  food,  (2) 
water,  (3)  air,  (4)  proper  temperature.  Study  of  a  single  plant  or  animal  in 
relation  to  its  environment.  Problems  of  city  government :  (a)  storage,  pres- 
ervation and  distribution  of  foods,  (6)  water  supply,  (c)  overcrowded  tene- 
ments, (d)  street  cleaning,  (e)  clean  schools.  Biological  problems  in  city 
government. 

Second  week.  Interrelations  between  Plants  and  Animals.  Plants  furnish 
food,  clothing,  shelter,  and  medicine.  Animals  use  food,  shelter.  Man'a 
use  of  plants  as  above.  Man's  use  of  animals  as  above.  Plant  and  animal 
industries.     Use  of  balanced  aquarium  as  illustrative  material. 

Third  week.  Destruction  of  Food  and  Other  Things  by  Mold.  Home  exper- 
iment. Conditions  favorable  to  growth  of  mold.  Food,  moisture,  tempera- 
ture.    Destruction  of  commodities  by  mold  :  food,  leather,  clothing. 

Fourth  week,  fifth  week.  Destruction  of  Foods  by  Bacteria.  Experiment. 
To  show  where  bacteria  are  found.  Soil,  dust,  water,  milk,  hands,  mouth. 
Use  and  harm  of  decay.  Relation  to  agriculture.  Experiment.  Conditions 
favorable  and  unfavorable  to  growth  of  bacteria :  boiling,  cold,  sugar,  salt. 
Bacteria  in  relation  to  disease  briefly  mentioned.     Bacteria  in  industries. 

Sixth  week.  Use  of  Stored  Food  by  Young  Green  Plant  :  (a)  for  energy,  (b)  for 
construction  of  tissue.  Experiment.  Structure  of  bean  seed.  Draw  to  show 
outer  coat,  cotyledon,  hypocotyl,  and  plumule.  Test  for  starch  and  sugar 
(grape).  Test  for  oil,  protein,  water,  mineral  matter.  Use  of  all  nutrients 
to  seedling. 

Seventh  week.  Other  Needs  of  Young  Plants.  Home  experiments  to  show 
(a)  temperature,  (b)  amount  of  water  most  favorable  to  germination. 
Experiment.  To  show  need  of  oxygen.  To  show  that  germinating  seeds  give 
off  carbon  dioxide.  Proof  of  presence  of  carbon  dioxide  in  breath.  The 
needs  of  a  young  plant  compared  with  those  of  a  boy  or  girl. 

Eighth  week.  Digestion  in  Seedling.  Structure  of  corn  grain.  Experiment. 
To  show  that  starch  is  digested  in  a  growing  seedling  (corn).  Experiment. 
To  show  that  diastase  digests  starch.    Discussion  of  experiments. 

Ninth  week.  What  Plants  take  from  the  Soil  and  How  they  do  This. 
Use  of  roots.  Proof  that  it  holds  plant  in  position,  takes  in  water  and 
mineral  matter,  and  in  some  cases  stores  food.  Influence  of  gravity  and 
water.  Labeled  drawing  of  root  hair.  Root  hair  as  a  cell  emphasized. 
Osmosis  demonstrated. 

Tenth  week.  Composition  of  the  Soil.  Demonstration  of  presence  of  mineral 
and  organic  substances  in  the  soil.  What  root  hairs  take  from  the  soil. 
Mineral  matter  necessary  and  why.  Importance  and  sources  of  nitrogen. 
Soil  exhaustion  and  its  prevention.  Nitrogen- fixing  bacteria.  Review 
bacteria  of  decay.     Rotation  of  crops. 


412  APPENDIX 

Eleventh  week.  Upward  Course  of  Materials  in  the  Stem.  Demonstration 
of  pea  seedlings  with  eosin  to  show  above.  Demonstration  of  evaporation  of 
water  from  a  leaf.  Action  of  stomata  in  control  of  transpiration.  Cellular 
structure  of  leaf.     Demonstration  of  elodea  to  show  cell. 

Twelfth  week.  Sun  a  Source  of  Energy.  Heliotropism.  Demonstration. 
Necessity  of  sunlight  for  starch  manufacture.  Necessity  of  air  for  starch 
manufacture.  By-products  in  starch  making.  Oil  manufacture  in  leaf. 
Protein  manufacture  in  plant.     Respiration. 

Thirteenth  week.  Reproduction.  Necessity  for  (a)  perpetuation,  (h)  regenera- 
tion. Study  of  a  typical  flower  to  show  sepals,  petals,  stamens,  pistil. 
Functions  of  each  part.  Cross  and  longitudinal  sections  of  ovary  shown 
and  drawn.  Emphasis  on  essential  organs.  Pollination,  self  and  cross. 
(Note.  At  least  one  field  trip  must  be  planned  for  the  month  of  May.  This 
trip  will  take  up  the  following  topics :  The  relations  between  flowers  and 
insects.  The  food  and  shelter  relation  between  plants  and  animals.  Recog- 
nition of  5  to  10  common  trees.  Need  of  conservation  of  forests.  An 
extra  trip  could  well  be  taken  to  give  child  a  little  knowledge  and  love  for 
spring  flowers  and  awakening  nature.) 

Fourteenth  week.  Study  of  the  Bee  or  Butterfly  with  Reference  to 
Adaptations  for  Insect  Pollination.  Study  of  an  irregular  flower  to 
show  adaptations  for  insect  visitors.  Fertilization  begun.  Growth  of 
pollen  tubes. 

Fifteenth  week.  Fertilization  Completed.  Use  of  chart  to  show  part  played 
by  egg  and  sperm  cell.  Ultimate  result  the  formation  of  embryo  and  its 
growth  under  favorable  conditions  into  young  plant.  Relation  of  flower  and 
fruit,  pea,  or  bean  used  for  this  purpose.  Development  of  fleshy  fruit.  Apple 
used  for  this  purpose. 

Sixteenth  week.  Maturing  of  Parts  and  Storing  of  Food  in  Seed  and  Fruit. 
The  devices  for  scattering  the  seeds  and  relation  to  future  plants.  Resume 
of  processes  of  nutrition  to  show  how  materials  found  in  fruit  and  seed  are 
obtained  by  the  plant. 

Seventeenth  week.  Plant  Breeding.  Factors :  (a)  selective  planting,  (h)  cross- 
pollination,  (c)  hybridizing.  Heredity  and  variation  begun.  Darwin  and 
Burbank  mentioned. 

Eighteenth  and  nineteenth  weeks.  The  Natural  Resources  of  Man  :  Soil, 
Water,  Plants,  Animals.  The  relation  of  plant  life  to  the  above  factors  of 
the  environment.  The  relation  of  insects  to  plants  (forage  and  other  crops) 
and  the  relation  of  birds  to  insects.  Need  for  conservation  of  the  helpful 
factors  in  the  environment  of  plants.  Attention  called  to  some  native  birds 
as  insect  and  wood  destroyers. 

Twentieth  week.    Review  and  Examinations. 


Second  Term 

First  week.  The  Balanced  Aquarium.  Study  of  conditions  producing  this. 
The  r61e  of  green  plants,  the  role  of  animals.  What  causes  the  balance. 
How  the  balance  may  be  upset.  The  nitrogen  cycle.  What  it  means  in  the 
world  outside  the  aquarium.  Symbiosis  as  opposed  to  parasitism.  Ex- 
amples. 


APPENDIX  413 

Second  week.  Study  of  the  Paramecium.  Study  of  a  hay  infusion  to  show  how 
environment  reacts  upon  animals.  Relation  to  environment.  Study  of 
cell  under  microscope  to  show  reactions.  Structure  of  cell.  Response  to 
stimuli,  function  of  cilia,  gullet,  nucleus,  contractile  vacuoles,  food  vacuoles, 
asexual  reproduction.  Drawings  to  show  how  locomotion  is  performed, 
general  structure.     Copy  chart  for  fine  structure. 

Third  week.  A  Bird's-eye  View  of  the  Animal  Kingdom.  One  day.  Develop- 
ment of  a  multicellular  organism.  (Use  models.)  One  day.  Physiological 
division  of  labor.  Tissues,  organs.  Functions  common  to  all  animals. 
Illustrative  material.  Optional  trip  to  museum  for  use  of  illustrative 
material  to  illustrate  the  principal  characteristics  of  (a)  a  simple  metazoan, 
sponge,  or  hydrazoan,  (6)  a  segmented  worm,  (c)  a  crustacean  (Decapod), 
(d)  an  insect,  (e)  a  moUusk  and  echinoderm,  (/)  vertebrates.  (Differences 
between  vertebrates  and  invertebrates.)  The  characteristics  of  the  verte- 
brates. Distinguish  between  fishes,  amphibia,  reptiles,  birds,  mammals. 
Two  days  for  discussion.  Man's  place  in  the  animal  series,  elementary  dis- 
cussion of  what  evolution  means. 

Fourth  week.     The    Economic    Importance    of    Animals.     Uses    of    animals : 

(1)  As    food.      Directly :    fish,    shellfish,    birds,    domesticated    mammals. 

(2)  Indirectly  as  food :  protozoa,  Crustacea.  (3)  They  destroy  harmful 
animals  and  plants.  Snakes  —  birds;  birds  —  insects;  birds — weed  seeds; 
herbivorous  animals — weeds.  (4)  Furnish  clothing,  etc.  Pearl  buttons, 
etc.  (5)  Animal  industries,  silkworm  culture,  etc.  (6)  Domesticated 
animals. 

Animals  do  harm:  (1)  To  gardens.  (2)  To  crops.  (3)  To  stored  food; 
examples,  rats,  insects,  etc.  (4)  To  forest  and  shade  trees.  (5)  To  human 
life.  Disease:  parasitism  and  its  results,  —  examples,  from  worms,  etc. ;  dis- 
ease carriers  fly,  etc.     Preventive  measures.     Methods  of  extermination. 

References  to  Toothaker's  Commercial  Raw  Materials.     Use  one  day  for 
laboratory  work  from  references. 

Fifth  week.  The  Study  of  a  Water-breathing  Vertebrate.  Two  days. 
The  fish,  adaptations  in  body,  fins,  for  food  getting,  for  breathing.  Struc- 
ture of  gills  shown.  Laboratory  demonstration  to  show  how  water  gets  to 
the  gills.  Drawings.  Outline  of  fish,  gills.  Required  trip  to  aquarium. 
Object,  to  see  fish  in  environment.  One  day.  Home  work  at  market. 
Why  are  some  fish  more  expensive  than  others.  Economic  importance  of 
fish.  Relation  of  habits  of  (a)  food  getting,  (b)  spawning  to  catching  and 
extermination  of  fish.  Two  days.  Means  of  preventing  overfishing,  stock- 
ing, fishing  laws,  artificial  fertilization  of  eggs,  methods.  Development  of 
fish  egg.     Comparison  with  that  of  frog  and  bird. 

Sixth  week.  The  Factors  underlying  Plant  and  Animal  Breeding.  Study 
of  pupils  in  class  to  show  heredity  and  variation.  Conclusion.  Animals 
tend  to  vary  and  to  be  like  their  ancestors.  Heredity,  role  of  sex  cells, 
chromosomes.  Principles  of  plant  breeding.  Selective  planting,  hybridiz- 
ing, work  of  Darwin,  Mendel,  De  Vries,  and  Burbank.  Methods  and  results. 
Animal  breeding,  examples  given,  results.  Improvement  of  man:  (1)  by 
control  of  environment,  (a)  example  of  clean-up  campaign,  1913  ;  (2)  by  con- 
trol of  individual,  personal  hygiene,  and  control  of  heredity.  Eugenics. 
Examples  from  Davenport,  Goddard,  etc. 


414  APPENDIX 

Seventh  week.  The  Human  Machine.  Skin,  bones  and  muscles,  function  of 
each.  Examples  and  demonstration  with  skeleton.  Organs  of  body  cavity  ; 
show  manikin.     Work  done  by  cells  in  body. 

Eighth  week.  Study  of  Foods  to  determine  :  (a)  nutritive  value.  Exercise  with  food 
charts  to  determine  foods  rich  in  water,  starch,  sugar,  fats,  proteins,  mineral 
salts,  refuse.  One  day.  -(6)  Nutritive  value  of  foods  as  related  to  work, 
age,  sex,  environment,  cost,  and  digestibility.  Foods  compared  to  determine 
what  is  really  a  cheap  food. 

Ninth  week.  How  the  Fuel  Value  of  Food  has  been  Determined.  The 
dietaries  of  Atwater,  Chittenden,  and  Voit.  The  100-calorie  portion  table 
and  its  use. 

Tenth  week.  The  Application  of  the  100-Calorie  Portion  to  the  Making 
of  the  Daily  Dietaries.  Luncheon  dietaries.  A  balanced  dietary  for 
pupil  for  one  day.     Family  dietaries.     Relation  to  cost.     Reasons  for  this. 

Eleventh  week.     Food  Adulterations.     Tests.     Drugs  and  the  alcohol  question. 

Twelfth  week.  Digestion.  The  alimentary  canal  of  frog  and  of  man  compared. 
Drawings.  (One  day.)  The  work  of  glands.  Work  of  salivary  gland. 
Enzymes,  internal  secretions.  Experiments  to  show  (a)  digestion  of  starch 
by  saliva,  (b)  digestion  of  proteins  by  gastric  or  pancreatic  juice,  (c)  emulsi- 
fication  of  fats  in  the  presence  of  an  alkaline  medium.  Functions  of  other 
digestive  glands.  Movements  of  stomach  and  intestine  discussed  and  ex- 
plained. 

Thirteenth  week.  Absorption.  How  it  takes  place,  where  it  takes  place.  Pas- 
sage of  foods  into  blood,  function  of  liver,  glycogen. 

Fourteenth  week.  The  Blood  and  its  Circulation.  Composition  and  functions 
of  plasma,  red  corpuscles,  colorless  corpuscles,  blood  plates,  antibodies. 
The  lymph  and  work  of  tissues.  The  blood  and  its  method  of  distribu- 
tion. Heart  a  force  pump.  Demonstration.  Arteries,  capillaries  (demon- 
stration), veins.     Hygiene  of  exercise. 

Fifteenth  week.  What  Respiration  does  for  the  Body.  The  apparatus  used. 
Changes  of  blood  within  lungs,  changes  of  air  within  lungs.  Demonstration. 
Cell  respiration.  The  mechanics  of  respiration.  Demonstration.  Venti- 
lation, need  for,  explain  proper  ventilation.  Demonstration.  Hygiene  of 
fresh  air  and  proper  breathing.     Dusting,  sweeping,  etc. 

Sixteenth  week.  Excretion,  Organs  of.  Skin  and  kidneys,  regulation  of  body 
heat.  Colds  and  fevers.  Proper  care  of  skin,  hygiene.  Summary  of 
blood  changes  in  body.     Explanation  of  same. 

Seventeenth  week.  Body  Control  and  Habit  Formation.  Nervous  system,  nerve 
control.  The  neuron  theory,  brain  psychology  explained  in  brief.  Habits 
and  habit  formation.     Hygiene  of  sense  organs. 

Eighteenth  and  nineteenth  weeks.  Civic  Hygiene  and  Sanitation.  The  Im- 
provement of  One's  Environment.  Civic  conditions  discussed.  Water, 
milk,  food  supplies.  Relation  to  disease.  How  safeguarded.  How  help  im- 
prove conditions  in  city. 

Twentieth  week.    Review  and  Examinations. 


APPENDIX  415 

HYGIENE   OUTLINE 

(This  outline  may  be  introduced  with  Plant  Biology,  or,  better,  may  come  as  application  of 
the  work  in  Second- term  Biology.) 

The  Environment.  Changes  for  betterment  under  control.  How  a  city  boy 
may  improve  his  environment :  by  proper  clothing,  proper  food  and  preparation  of 
food,  by  care  in  home  life  ;  by  sanitary  conditions  in  neighborhood  and  in  home. 

Review  of  Activities  of  Cell.  Irritability,  food  taking,  assimilation,  oxidation, 
excretion,  reproduction.  Similarity  of  functions  of  plant  and  animal  cells.  All 
cells  perform  these  functions.  Some  cells  perform  functions  especially  well,  e.g. 
contracting  muscle  cells.  All  cells  need  food  and  oxygen.  Some  must  have  this 
carried  to  them.  A  system  of  tubes  carries  blood  which  carries  food  and  oxygen. 
Food  must  be  prepared  to  get  into  the  blood.  Digestive  system  :  mouth,  teeth, 
stomach,  intestines,  glands,  and  digestive  juices.  Uses  of  above  in  preparing  food 
to  pass  into  the  blood.  Absorption  of  food  into  the  blood.  How  oxygen  gets  to 
the  cells.  Nose,  throat,  windpipe,  lungs ;  blood  goes  to  lungs  and  carries  away 
oxygen.  Excretion.  Cells  give  up  wastes  to  blood  and  these  wastes  taken  out  of 
blood  by  kidneys  and  other  glands  and  passed  out  of  body.  Sweat,  urine,  carbon 
dioxide. 

Certain  Kinds  of  Work  performed  by  Certain  Kinds  of  Cells.  Advantage 
of  this.  Cells  of  movement.  Muscles,  tissues.  Bones  as  levers  necessary  for  some 
movements.  This  especially  true  for  legs  and  arms.  Skeleton  also  necessary  for  pro- 
tection of  internal  organs  and  support  of  body.  Making  of  special  things  in  the 
body,  e.g.  digestive  juices  given  to  certain  cells  called  gland  cells.  Working  together 
or  coordination  of  different  organs  provided  for  by  nervous  system.  This  is  com- 
posed of  cells  which  are  highly  irritable  or  sensitive.  Collections  of  these  nerve 
cells  give  us  the  power  of  feeling  or  sensation  and  of  thinking. 

Dietetics.  Diet  influenced  by  age,  weight,  occupation,  temperature  or  climate, 
cheapness  of  food,  digestibility. 

Nutrients.  List  of  nutrients  found  in  seeds  and  fruits,  also  other  common  foods. 
Need  of  nutrients  for  human  body.  Nitrogenous  foods,  examples.  A  mixed  diet 
best. 

Digestion  and  Indigestion.  What  is  digestion  ?  Where  does  it  take  place  ? 
Causes  of  indigestion.  Eating  too  rapidly  and  not  chewing  food.  Eating  foods 
hard  to  digest.  Overeating.  Eating  between  meals.  Hard  exercise  immediately 
before  or  after  eating. 

Constipation.  A  condition  in  which  the  bowels  do  not  move  at  least  once  every 
day.  Dangers  of  constipation.  Poisonous  materials  may  be  absorbed,  causing 
lack  of  inclination  to  work,  headache.  Importance  of  regular  habits  of  emptying 
the  bowels.  Each  one  must  try  to  get  at  the  cause  of  constipation  in  his  own  case. 
Causes  of  constipation.  Lack  of  exercise,  improper  food,  not  drinking  enough  water, 
lack  of  laxative  food,  as  fruits;  lack  of  sleep,  lack  of  regular  habits.  Remedies. 
Avoid  use  of  drugs.  Half  hour  before  breakfast  a  glass  of  hot  water,  exercise  of 
abdominal  muscles,  laxative  foods,  form  habit  of  moving  bowels  after    breakfast. 

Hygiene  of  Circulation  and  Absorption.  How  digested  foods  get  to  the  cells. 
Absorption.  Definition.  The  passing  of  the  digested  food  into  the  blood.  How 
accomplished.  Blood  vessels.  In  walls  of  stomach  and  food  tube.  Membrane 
of  cells  separating  food  from  blood.  Food  passes  by  osmosis  through  the  membrane 
and  by  osmosis  through  the  thin  walls  of  the  blood  vessels. 


416  APPENDIX 

Circulation  of  Foods.  Blood  contains  foods,  oxygen,  and  A^aste  materials. 
Heart  pumps  the  blood,  blood  vessels  subdivide  until  very  small  and  thin,  so  food, 
etc.,  passes  from  them  to  cells.     Hygiene  of  the  heart. 

Transpiration  AND  Excretion.  Skin,  function  in  excretion.  Bathing.  Care  of 
skin.  Hot  baths.  Bathe  at  least  twice  a  week.  Cold  baths,  how  taken.  Bath- 
tub not  a  necessity.  Effect  of  latter  on  educating  skin  to  react.  Relation  to 
catching  cold. 

Care  of  Scalp  and  Nails.  Scalp  should  be  washed  weekly.  If  dandruff  present, 
wash  often  enough  to  keep  clean.  Baldness  often  results  from  dandruff.  Finger 
nails  cut  even  with  end  of  fingers  and  cleaned  daily  with  scrub  brush. 

Hygiene  of  Respiration.  Definition  of  respiration.  Object  of  respiration. 
(Connection  between  circulation  and  respiration.)  Necessity  of  oxygen.  Organs 
of  respiration.  Lungs  most  important.  Deep  breath,  function.  Ventilation, 
reasons  for.  Mouth  breathing.  Results.  Lessened  mental  power,  nasal  catarrh, 
colds  easily  caught. 

Plants  harmful  to  Man.  Poison  ivy  and  mushrooms.  Treatment.  Poisoning. 
Send  for  physician.  Cause  vomiting  by  (1)  finger,  (2)  mustard  and  water.  (Note. 
An  unconscious  person  should  not  be  given  anything  by  the  mouth  unless  he  can 
swallow.)  Relation  of  yeasts  and  bacteria  to  man.  Fermentation  a  cause  of 
indigestion.     Relation  to  candy,  sirups,  sour  stomach,  formation  of  gas  causes  pain. 

Bacteria  of  Mouth  and  Alimentary  Canal.  Entrance  of  bacteria  by  mouth 
and  nose.  Nose  :  "  cold  in  the  head,"  grippe,  catarrh.  Mouth  :  decay  of  teeth,  ton- 
sillitis, diphtheria.  Germs  pass  from  one  person  to  another,  no  one  originates  germs 
in  himself.  Precautions  against  receiving  and  transferring  germs.  Common 
drinking  cups,  towels,  coins,  lead  pencils,  moistening  fingers  to  turn  pages  in  book  or 
to  count  roll  of  bills.  Tuberculosis  germs.  Entrance  by  mouth,  lungs  favorite 
place,  may  be  any  part  of  body.  Dust  of  air,  sweeping  streets,  watering  a  necessity. 
Spitting  in  streets  and  in  public  buildings.  Germs  of  typhoid  fever.  Entrance : 
water,  milk,  fresh  uncooked  vegetables,  oysters.  Thrive  in  small  intestines. 
Preventable.  Typhoid  epidemics,  methods  of  prevention  of  typhoid.  Conditions 
favorable  for  growth  of  specific  disease  germs.     Work  of  Boards  of  Health. 

Home  sanitary  conditions,  sunlight,  air,  curtains  and  blinds,  open  windows. 
Live  out  of  doors  as  much  as  possible.  Cleanliness.  Bare  walls  well  scrubbed 
better  than  carpets  and  rugs.  Lace  curtains,  iron  bedsteads,  one  thickness  of 
paper  on  walls.     Open  plumbing,  dry  cellars,  all  garbage  promptly  removed. 

This  outline  is  largely  the  work  of  Dr.  L.  J.  Mason  and  Dr.  C.  H.  Morse  of  the 
department  of  biology  of  the  De  Witt  Clinton  High  SchooL 


WEIGHTS,   MEASURES,   AND   TEMPERATURES 

As  the  metric  system  of  weights  and  measures  and  the  Centigrade  measurement 
of  temperatures  are  employed  in  scientific  work,  the  following  tables  showing  the 
Enghsh  equivalents  of  those  in  most  frequent  use  are  given  for  the  convenience  of 
those  not  already  familiar  with  these  standards.  The  values  given  are  approximate 
only,  but  will  answer  for  all  practical  purposes. 


Weight 


Measures  of  Length 


Kilogram 

kg. 

2\  pounds 

Gram     .    . 

gm. 

15J  grains  avoir- 
dupois. 

^  of  an  ounce 
avoirdupois. 

Capacity 


61  cubic  inches,  or 

a  little  more  than 

1    'quart,    U.    S. 

Licer      .    . 

1. 

measure. 

Cubic  cen- 

timeter . 

cc. 

Ib  of  a  cubic  inch. 

Metric 

English  Equivalents 

Kilometer 

km. 

f  of  a  mile. 

Meter    .    . 

m. 

39  inches. 

Decimeter 

dm. 

4  inches. 

Centimeter 

cm. 

f  of  an  inch. 

Millimeter 

mm. 

^  of  an  inch. 

The  next  table  gives  the  Fahrenheit  equivalent  for  every  tenth  degree  Centigrade 
from  absolute  zero  to  the  boiling  point  of  water.  To  find  the  corresponding  F.  for 
any  degree  C,  multiply  the  given  C.  temperature  by  nine,  divide  by  five,  and  add 
thirty-two.  Conversely,  to  change  F.  to  C.  equivalent,  subtract  thirty-two,  multi- 
ply by  five,  and  divide  by  nine. 


Cent. 


Fahr.  Cent. 


Fahr. 


Cent. 


Fahr.   Cent. 


Fahr 


100  . 

.    .  212 

50  .    . 

.  122 

0  .    . 

.       32 

-    50  .     .     .  -    58 

90  . 

.  194 

40  .    . 

.  104 

-  10  .     . 

14 

-  100  .    .     .  -  148 

80  . 

.    .  176 

.  158 

30  .    , 
20  .    . 

.    86 
.    68 

-20  .    . 
-30  .    . 

.  -    4 
.  -22 

70  . 

Absolute  zero 

60  .    . 

.  140 

10  .    . 

.    50 

-40  .    . 

.   -40 

-  273  .    .    .  -  459 

HUNTER, 

CIV.    BI 

.  —  27 

417 

418  APPENDIX 

Laboratory  Equipment 

The  following  articles  comprise  a  simple  equipment  for  a  laboratory  class  of 
ten.  The  equipment  for  larger  classes  is  proportionately  less  in  price.  The  follow- 
ing articles  may  be  obtained  from  any  reliable  dealer  in  laboratory  supplies,  such  as 
the  Bausch  and  Lomb  Optical  Company  of  Rochester,  N.Y.,  or  the  Kny-Scheerer 
Company,  404,  410  West  27th  Street,  New  York  City  :  — 

1  balance.  Harvard  trip  style,  with  weights  on  carrier. 

1  bell  jar,  about  365  mm.  high  by  165  mm.  in  diameter. 
10  wide  mouth  (salt  mouth)  bottles,  with  corks  to  fit. 

10  25  c.c.  dropping  bottles  for  iodine,  etc. 
25  250  c.c.  glass-stoppered  bottles  for  stock  solutions. 
100  test  tubes,  assorted  sizes,  principally  6"  X  |". 
50  test  tubes  on  base  (excellent  for  denaonstrations). 

2  graduated  cylinders,  one  to  100  c.c,  one  to  500  c.c. 

1  package  filter  paper  3(X)  mm.  in  diameter. 
10  flasks,  Erlenmeyer  form,  500  c.c.  capacity. 

2  glass  funnels,  one  50,  one  150  mm.  in  diameter. 

30  Petri  dishes,  100  mm.  in  diameter,  10  mm.  in  depth. 
10  feet  glass  tubing,  soft,  sizes  2,  3,  4,  5,  6,  assorted. 

1  aquarium  jar,  10  liters  capacity. 

2  specimen  jars,  glass  tops,  of  about  1  liter  capacity. 
10  hand  magnifiers,  vulcanite  or  tripod  form. 

2  compound  demonstration  microscopes  or  1  more  expensive  compound  micro* 
scope. 
300  insect  pins,  Klaeger,  3  sizes  assorted. 
10  feet  rubber  tubing  to  fit  glass  tubing,  size  |  inch. 

1  chemical  thermometer  graduated  to  100°  C. 
15  agate  ware  or  tin  trays  about  350  mm.  long  by  100  wide. 
1  gal.  95  per  cent  alcohol.     (Do  not  use  denatured  alcohol.) 
1  set  gram  weights,  1  mg.  to  100  g.  2  books  test  paper,  red  and  blue. 

1  razor,  for  cutting  sections.  10  Syracuse  watch  glasses. 

1  box  rubber  bands,  assorted  sizes.  1  steam  sterilizer  (tin  will  do). 

1  support  stand  with  rings.  1  spool  fine  copper  wire. 

1  test  tube  rack.  1  alcohol  lamp.  6  oz.  nitric  acid. 

5  test  tube  brushes.  1  gross  slides.  6  oz.  ammonium  hydrate. 

10  pairs  scissors.  100  cover  slips  No.  2.  6  oz.  benzole  or  xylol. 

10  pairs  forceps.  1  mortar  and  pestle.  6  oz.  chloroform. 

20  needles  in  handles.  2  bulb  pipettes.  |  lb.  copper  sulphate. 

10  scapels.  1  liter  formol.  ^  lb.  sodium  hydroxide. 

12  mason  jars,  pints.  1  oz.  iodine  cryst.  |  lb.  rochelle  salts. 

12  mason  jars,  quarts.  1  oz.  potassium  iodide.       6  oz.  glycerine. 

The  materials  for  Pasteur's  solution  Sach's  nutrient  solution  can  best  be  obtained 
from  a  druggist  at  the  time  needed  and  in  very  small  and  accurately  measured 
quantities. 

The  agar  or  gelatine  cultures  in  Petri  dishes  may  be  obtained  from  the  local 
Board  of  Health  or  from  any  good  druggist.  These  cultures  are  not  difficult  to 
make,  but  take  a  number  of  hours'  consecutive  work,  often  diflicult  for  the  average 
teacher  to  obtain.  Full  directions  how  to  prepare  these  cultures  will  be  found  in 
Hunter's  Laboratory  Problems  in  Civic  Biology. 


INDEX 

(Illustrations  are  indicated  by  page  numerals  in  bold-faced  tj'pe.) 


Absorption,  definition,  270 ; 

of  digested  foods,  308,  309. 
Accommodation  of  eye,  361. 
Acetanilid,  295. 
Action  of  the  heart,  319. 
Adaptations,  24; 

in  bee,  36 ; 

in  birds,  189; 

in  fish,  232 ; 

in  frog,  241 ; 

in  mammalia,  192. 
Adenoids,  340,  395. 
Adulteration  in  foods,  288. 
Air,  and  bacteria,  145 ; 

composition  of,  20 ; 

fresh,  337 ; 

needed  in  germination,  66  ; 

necessary  in  starch  making,  91 ; 

passages  in  lungs,  330  ; 

use  to  plants  and  animals,  21. 
Albumin,  62. 
Alcohol,  a  food,  289 ; 

a  poison,  291. 

and  ability  to  resist  disease,  363 ; 

and  ability  to  work,  368 ; 

and  body  heat,  345 ; 

and  crime,  371,  372; 

and  digestion,  311 ; 

and  duration  of  life,  370 ; 

and  efficiency,  369 ; 

and  heredity,  372 ; 

and  intellectual  ability,  364 ; 

and  kidneys,  346 ; 

and  living  matter,  291 ; 

and  memory,  365 ; 

and  mental  ability,  366 ; 

and  nervous  system,  362 ; 

and  organs  of  special  sense,  362 ; 

and  pauperism,  371 ; 

and  resistance,  327 ; 


Alcohol,  and  respiration,  346 ; 

and  the  blood,  327  ; 

and  treatment  of  disease,  364 ; 

effect  on  circulation,  327 ; 

effect  on  eye,  361 ; 

effect  on  liver,  312 ; 

produces  poisons,  347. 
AlgsD,  176. 
Alfalfa  plant,  151. 
Alimentary  canal,  297. 
Alkali,  306. 
Alkalinity,  298. 
Alligator,  230. 
Ambergris,  205. 
Ammonium  hydrate,  61. 
Amoeba,  170,  182,  332. 
Amphibia,  186,  187 ; 

as  food,  202. 
Anal  fin  of  fish,  233. 
Angiosperms,  176. 
Animals,  as  disease  carriers,  227 ; 

breeding  of,  259 ; 

domesticated,  260 ; 

functions  of,  48,  180 ; 

need  plants,  34 ; 

oils  of,  205 ; 

parasitic,  227 ; 

series,  182 ; 

that  prey  upon  man,  230 ; 

use  to  man,  17  ; 

use  to  plants,  34. 
Annual  rings,  98. 
Anopheles,  217,  218. 
Anosia  plexippus,  32. 
Anther,  36. 

Antibodies,  uses  of,  316. 
Antiseptics,  157. 
Antitoxin,  157,  391. 
Anura,  188. 
AnvU,  359. 


419 


420 


INDEX 


Aorta,  320. 
Apoplexj%  328. 
Appendages  of  the  fisii,  233. 
Appendicular  skeleton,  268. 
Appendix,  309. 
Apples,  56,  124. 
Aqueous  humor,  361. 
Arachnida,  185. 
Arteries,  318 ; 

structure  of,  323. 
Arthropods,  185. 
Artificial,  cross- pollination,  46; 

propagation  of  fishes,  240 ; 

respiration,  340 ; 

selection,  253. 
Asexual  reproduction,  174. 
Assimilation  in  plants,  103. 
Attention,  effect  of  alcohol,  364. 
Audubon,  211. 
Auricle  of  human  heart,  319; 

of  fish  heart,  236. 
Automatic  activity,  348,  354. 
Axial  skeleton,  268. 

Bacillus,  142. 
Bacteria,  134 ; 

and  fermentation,  150 ; 

cause  decay,  149 ; 

cause  disease,  151 ; 

effect  on  food,  144  ; 

growth  of,  145 ; 

isolating  a  pure  culture,  142 ; 

nitrogen  fixing,  80,  81,  151,  152; 

of  decay,  144 ; 

relation  to  man,  16 ; 

size  and  form,  142,  143  ; 

useful,  150 ; 

where  found,  139,  141. 
Bacteriology,  16. 
Bad  posture,  270. 
Balanced,  aquarium,  159,  160; 

diet,  285. 
Barbels  of  fish,  234. 
Barberry  embryo,  103. 
Bark,  use  of,  98. 
Barrier,  natural,  25. 
Bast,  97. 

Beans,  as  food,  62. 
Beans,  peas,  55. 


Beans,  seedlings,  63. 
Bedroom,  care  of,  374. 
Bee,  adaptations,  36 ; 

head  of,  38 ; 

mouth  parts,  38. 
Beer  and  wine  making,  137. 
Benedict's  test,  68. 
Benzoic  acid,  148. 
Beverages  and  condiments,  124. 
Biceps,  269. 

Bichloride  of  mercury,  148. 
Bile,  functions  of,  306,  307. 
Biology,  definition,  15 ; 

relation  to  society,  18. 
Birds,  189; 

as  food,  202 ; 

classification,  191 ; 

development,  246 ; 

eat  insects,  209 ; 

eat  weed  seeds,  210; 

embryo,  246,  247. 
Bismuth,  304. 
Bison,  192. 
Black  Death,  227. 
Blade  of  leaf,  85. 
Blastula,  177. 

Blood,    amount    and    distribution, 
318; 

changes  in  lungs,  330 ; 

circulation  of  man,  318 ; 

clotting,  314 ; 

composition,  314 ; 

effect  of  alcohol,  327 ; 

function,  313 ; 

plates,  315 ; 

poisoning,  156 ; 

temperature,  318; 

vessel  of  skin,  344. 
Blubber,  205. 
Blue  crab,  199. 

Board  of  health,  functions,  389. 
Body,  a  machine,  348 ; 

cavity,  270 ; 

heat  and  alcohol,  345 ; 

of  fish,  232. 
Bony  fish,  187. 
Boracic  acid,  148. 
Borax,  148. 
Brain,  of  fish,  237 ; 


4 


I 


INDEX 


421 


Brain,  of  man,  351. 
Bread,  making,  139; 

mold,  133. 
Bream,  233. 
Breathing,  333 ; 

and  tight  clothing,  339 ; 

hygienic  habits,  338 ; 

in  leaf,  93 ; 

of  fish,  234 ; 

of  frog,  242 ; 

of  vertebrates,  232 ; 

rate  of,  334. 
Breeding  of  animals,  259. 
Bright's  disease,  346. 
Bronchi,  330. 
Bronchial  tubes,  330. 
Bruises,  345. 
Bryophytes,  176. 
Bubonic  plague,  227. 
Budding,  255,  256. 
Bumblebees,  37. 
Burbank,  Luther,  406. 
Burns,  treatment  of,  345. 
Butter  and  eggs,  38,  39. 

Calorie,  portion,  286 ; 

requirement,  282. 
Calyx,  35. 
Cambium  layer,  98. 
Canning,  145. 
Cannon,  Prof.,  304. 
CapiUaries,  318,  323 ; 

circulation  in,  322 ; 

of  fish,  236. 
Carbohydrates,  60,  273. 
Carbolic  acid,  149. 
Carbon  and  oxygen  cycle,  161. 
Carbon  dioxide,  test  for,  64. 
Care  of  milk  supply,  380,  383. 
Carnivorous,  230. 
Caudal  fin  of  fish,  233. 
Cause  of  dyspepsia,  310. 
Cells,  50; 

as  units,  171 ; 

division,  51 ; 

mucous,  299 ; 

of  pond  scum,  173  ; 

reproduction  of,  50 ; 

respiration,  332 ; 


Cells,  tissue,  179; 

work  of,  270. 
Cephalothorax,  185. 
Cerebellum,  352. 

Cerebro-spinal  nervous  system,  350. 
Cerebrum,  351. 
Cestodes,  227. 
Changes,  of  blood  in  lungs,  330 ; 

of  air  in  lungs,  331. 
Characters,  determiners  of,  258. 
Chelonia,  188. 
Chemical,  compounds,  20 ; 

elements,  20 ; 

of  human  body,  21. 
Chestnut  canker,  131. 
China,  deforestation  in,  108. 
Chittenden  table,  311. 
Chloral,  293. 

ChlorophyU  bodies,  50,  90. 
Chloroplasts,  90. 
Chromosomes,  50 ; 

and  heredity,  251. 
Chrysalis,  33. 
Cilia,  171. 
Circulation,  effect  of  alcohol,  327 ; 

effect  of  exercise,  326  ; 

effect  of  tobacco,  328 ; 

in  fish,  frog,  man,  321,  322; 

in  stem,  99,  100,  101 ; 

of  blood  of  man,  318 ; 

of  fish,  236 ; 

of  frog,  243 ; 

portal,  322 ; 

pulmonary,  320; 

systemic,  320. 
City's  need  for  trees,  115. 
Civic  hygiene,  388. 
Clams,  200. 
Classification,  of  birds,  191 ; 

of  plants,  176. 
Cloaca  of  frog,  243. 
Clothing,  203. 
Clotting  of  blood,  314. 
Coal,  64. 
Cobra,  230. 
Cocaine,  293. 
Coccus  bacteria,  142. 
Cochineal  and  lac,  208. 
Cochlea,  359. 


422 


INDEX 


Codling  moth,  215. 
Ccelenterates,  183. 
Cold-blooded  animals,  318 ; 

effect  of,  23. 
Cold  storage,  147. 
Colds  and  fevers,  343. 
Coleoptera,  32. 
Collecting  ashes,  387. 
Colonies  of  bacteria,  141 ; 

of  trilliums,  175. 
Colorless  corpuscles,  313 ; 

structm^e,  315 ; 

function,  316. 
Common   foods   contain   nutrients, 

275. 
Comparison,  of  food  tube  of  frog  and 
man,  297 ; 

of  mold,  yeast  and  bacteria,  143 ; 

of    starch    making    and    milling, 
92. 
Complemental  air,  334. 
Complex  one-celled  animals,  171. 
Composition,  of  milk,  273,  280 ; 

of  plasma,  313 ; 

of  soil,  77. 
Compound  eyes  of  bumblebee,  37, 

38. 
Conservation,  of  food  fish,  239  ; 

of  fur-bearing  animals,  204  ; 

of  our  natural  resources,  17. 
Constipation,  310. 
Constrictor  kilHng  a  mouse,  213. 
Contagious  diseases,  152. 
Convolutions,  352. 
Corn,  120,  121 ; 

germinated  grain  cut  lengthwise, 
69; 

long  section  of  ear,  67 ; 

structure  of  grain,  66. 
Cornfield,  44. 
Corolla,  35. 

Corpuscles,  colorless  and  red,  313. 
Cost  of  food  and  diet,  281,  283  ; 

of  parasitism,  263. 
Cotton,  125 ; 

boll  weevil,  126,  127,  214. 
Cotyledons,  59 ; 

food  in,  60. 
Crab,  199. 


Crayfish,  184. 
CrocodUe,  230. 
Crocodilia,  189. 
Crustacea,  185. 
Culex,  218,  218. 
Culture  medium,  140. 
Cuts  and  bruises,   treatment,   326, 
345. 

Daily  calorie  requirement,  282  ; 

fuel  needs  of  body,  284. 
Dandelion,  whorled  leaves,  90. 
Darwin,  Charles,  40,  404. 
Darwin  and  natural  selection,  253. 
Deaths,  table,  312. 
Decay  caused  by  bacteria,  149. 
Decayed  teeth,  396. 
Defects  in  eye,  361. 
Deforestation  in  China,  108. 
Dendrites,  351. 
Department  of  Agriculture,  work  of, 

255. 
Department     of     street     cleaning, 

387. 
Determiners,  251 ; 

of  character,  258. 
Development,  of  apple,  56 ; 

of  bird,  246 ; 

of  egg,  178 ; 

of  trout,  238 ; 

of  mammal,  247 ; 

of  salmon,  241 ; 

of  simple  animal,  177. 
Diagram  of  frog's  tongue,  242 ; 

of  gills  of  fish,  235 ; 

of  neuron,  351 ; 

of  wall  small  intestine,  307. 
Diaphragm,  270,  297. 
Diastase,  101,  300; 

action  on  starch,  69. 
Diet,  and  cost  of  food,  281 ; 

and  digestibility,  281 ; 

balanced,  285 ; 

relation  of  age,  280  ; 

relation  of  environment  to,  280  ; 

relation  to  sex,  280 ; 

relation  of  work  to,  277 ; 

the  best,  284. 
Dietary,  the  best,  282. 


i 


INDEX 


423 


Digested  food,  absorption  of,  308. 
Digestibility  and  diet,  281. 
Digestion,  68,  100,  181 ; 

effect  of  alcohol,  311 ; 

definition  of,  270 ; 

in  stem,  99 ; 

in  stomach,  304; 

of  starch,  299 ; 

purpose  of,  69,  296. 
Digestive  system  of  fish,  235. 
Digestive    tract  of  frog   and   man, 

297. 
Diphtheria,  152. 
Dipnoi,  187,  236. 
Diptera,  31. 

Discoverers  of  living  matter,  398. 
Disease,  and  alcohol,  312 ; 

and  bacteria,  151 ; 

carriers,  animals,  226 ;    . 

carriers,  flies,  222 ; 

carriers,  insects,  225 ; 

caused  by  bacteria,  152  ; 

caused  by  protozoa,  172  ; 

effect  of  alcohol,  327 ; 

of  nose  and  throat,  340 ; 

protozoan,  221. 
Disinfectants,  148. 
Division  of  labor,  178,  267. 
Dog,  skeleton,  185. 
Domesticated  animals,  203,  260. 
Dominant  characters,  258. 
Dormant,  22. 
Dorsal,  186 ; 

fin,  233. 
Drugs,  use  and  abuse,  294. 
Duff,  113. 

Dyspepsia,    cause   and    prevention, 
310. 

Ear,  section,  359. 
Echinoderms,  184. 
Economic  value  of  green  plants,  117  ; 
importance  of  spawning  habits  of 
fishes,  239. 
Ectoderm,  177. 
Effect  of  light  on  leaves,  88. 
Efficiency  of  a  week,  370. 
Egg,  177,  246. 
Egg-laying  habits  of  fishes,  238. 


Ehrlich,  Paul,  403. 
Elasmobranchs,  187. 
Elements,  chemical,  20,  21. 
Elodea,  49,  50. 
Embryo,  58,  59,  103 ; 

of  bird,  247 ; 

of  mammal,  247. 
Emulsion,  306. 
Endoderm,  177. 
Endoskeleton,  definition,  237. 
Endosperm,  67. 
Enemies  of  forests,  113,  114. 
Energy,  64 ; 

of  a  tree,  94 ; 

source  of,  88. 
English  sparrow,  212. 
Environment,  19,  19 ; 

care  and  improvement  of,  26 ; 

changes  in,  25 ; 

determines    kind    of    plants    and 
animals,  23,  23,  24; 

normal,  28 ; 

of  man,  26,  266 ; 

natural,  25 ; 

relation  to  diet,  280 ; 

what    plants    and    animals    take 
from,  21. 
Enzymes,  68,  101,  298. 
Epicotyl,  59. 
Epidermis,  86. 
Epithelial  layer,  308. 
Epithelium,  179. 
Erosion,  prevention  of,  106,  108 ; 

at  Sayre,  Pa.,  106. 
Essential  organs,  36. 
Esophagus,  302. 
Eugenics,  261. 
Eustachian  tubes,  300,  359. 
Euthenics,  264. 
Evaporation,  99 ; 

of  water,  85,  86,  87. 
Evolution,  194,  195. 
Excretion,  181,  270,  332; 

organs  of,  340 ; 

in  plants,  103. 
Exercise  and  circulation,  326 ; 

and  health,  339. 
Exoskeleton,  185,  237. 
Extermination  of  birds,  211. 


424 


INDEX 


Eye,  compound,  30 ; 

defects  in,  361 ; 

section  of,  360, 
Eyestrain,  395. 

Factory  inspection,  379. 
Fallowing,  82. 
Fatigue,  326 ; 

and  nerve  cells,  356. 
Fats  and  oils,  60,  273. 
Fehling's  solution,  68,  299. 
Fermentation,  135,  136,  150. 
Fertilization,  of  fish  eggs,  240 ; 

of  flower,  54. 
Fibers,  vegetable,  127. 
Fibrin,  315. 
Fibrinogen,  315. 
Fig  insect,  43. 
Filament,  36. 

Filter  beds  at  Albany,  N.  Y.,  385. 
Fins,  233. 
Fishes,  186; 

artificial  propagation,  240 ; 

as  food,  201 ; 

body  of,  232 ; 

breathing,  234; 

circulation,  236,  321 ; 

digestive  system,  235 ; 

egg-laying  habits,  238 ; 

food  getting,  234 ; 

food  of,  237 ; 

gills,  234 ; 

heart,  236 ; 

migration,  238 ; 

nervous  system,  237 ; 

skeleton,  237 ; 

senses,  233 ; 

swim  bladder,  236. 
Fission,  170. 

Flagella  of  bacteria,  142. 
Flatworms,  183. 
Flax,  128. 
Flea,  225. 

Floral  envelope,  35. 
Flower,  fertilization  of,  54 ; 

lengthwise  section,  35 ; 

use  and  structure,  35. 
Fluid,  181. 
Fly,  a  disease  carrier,  222 ; 


Fly,  foot  of,  223 ; 

life  history,  222 ; 

typhoid,  223. 
Foods,  absorption  of,  309 ; 

adulteration,  288 ; 

amphibia  as,  202 ; 

birds  as,  202 ; 

cost  of,  283; 

fish  as,  201 ; 

fruits  and  seeds,  119; 

getting  of  fish,  234 ; 

in  cotyledons,  60 ; 

inorganic,  274 ; 

inspection,  380 ; 

is  alcohol  a  food,  289 ; 

leaves,  117,  118; 

making  in  green  leaf,  93 ; 

mammals  as,  202 ; 

of  animal  origin,  279 ; 

of  bacteria,  144 ; 

of  fishes,  237 ; 

of  insects,  33 ; 

of  plant  origin,  278 ; 

of  starfish,  216 ; 

reptiles  as,  202 ; 

roots  as,  119; 

stems  as,  118; 

taking,  181 ; 

tube  of  frog,  243  ; 

values,  tables,  276 ; 

waste  in  kitchen,  287 ; 

why  we  need,  272. 
Foraminifera,  182. 
Forestry,  113. 
Forest  destruction,  112,  113; 

fires,  112; 

of  North  Carolina,  105  ; 

other  uses,  109 ; 

protecting,  114; 

regions  of  United  States,  109. 
Formaldehyde,  148. 
Formation  of  habits,  354. 
Four  o'clock  embryo,  103. 
Fresh  air,  337. 
Frog,  adaptations  for  life,  241 ; 

and  man,  digestive  tract,  297 ; 

breathing,  242 ; 

ckculation,  243,  322 ; 

development  of,  244 ; 


INDEX 


425 


Frog,  diagram  of  tongue,  242 ; 

food  tube,  243 ; 

glands,  243 ; 

locomotion  of,  241 ; 

long  section,  243 ; 

metamorphosis,  245; 

nervous  system,  352 ; 

sense  organs,  242. 
Fruit,  a  typical,  55. 
Fruit  of  locust,  55. 
Fruits  and  seeds  as  foods,  119. 
Fruits,  how  scattered,  56. 
Fuel,  daily  needs,  284. 
Fuel  values  of  nutrients,  277. 
Fimctions,  of  all  animals,  180 ; 

of  an  animal,  48  ; 

of  bile,  307 ; 

of  blood,  313 ; 

of  cerebrum,  353 ; 

of  colorless  corpuscle,  316 ; 

of  lymph,  317 ; 

of  parts  of  plant,  48 ; 

of  red  corpuscle,  314. 
Fungi,  130,  176 ; 

moldlike,  135 ; 

of  our  homes,  132. 
Fur-bearing  animals,  204. 

Gall  bladder,  306 ; 

insects,  208. 
Gallflies,  43. 
Ganoids,  186,  187. 
Garbage  cans,  377. 
Garden  fruits,  123. 
Gastric  glands,  303 ; 

of  frog,  243. 
Gastric  juice,  303. 
Gastrula,  177,  178. 
Genus,  175. 
Geranium,  45. 
German  forest,  114. 
Germ  cells,  251. 
Germination,  of  bean,  63 ; 

of  pollen,  54. 
GiUs  of  fish,  234 ; 

rakers,  172,  234. 
Glands,  297,  298,  299 ; 

gastric,  303  ; 

lymph,  324; 


Glands  of  frog,  243 ; 

salivary,  299. 
Glomerulus,  341. 
Glottis  of  frog,  243. 
Glycogen,  307. 
Grafting,  256. 
Grains,  122. 

Grape  sugar,  test  for,  68. 
Gravity,  influence  on  root,  72. 
Green     plants,     economic     value, 
117; 

give  off  oxygen,  95  ; 

harmful,  127 ; 

make  starch,  90,  92. 
Groups  of  plants,  174. 
Guano,  82. 
Guard  cells,  88. 
Gullet,  297,  300,  301,  302,  303; 

of  frog,  243. 
Gymnosperms,  176. 
Gypsy  moth,  215. 

Habits,  354. 

Habitat  of  protozoa,  172. 

Habit  formation,  354. 

Haemoglobin,  314,  330. 

Hammer,  359, 

Hard  palate,  301. 

Harm  done  by  insects,  34,  225. 

Harmful  green  plants,  127 ; 

preservatives,  148. 
Hay  infusion,  163,  164. 
Head  of  a  bee,  38. 
Heart  a  force  pump,  320 ; 

diagram,  319 ; 

in  action,  319 ; 

internal  structure,  319 ; 

of  fish,  236 ; 

size,  position,  318. 
Heat,  and  bacteria,  145 ; 

effect  of,  22 ; 

output,  285. 
Heating  the  house,  375. 
Hemiptera,  32. 
Hen's  egg,  246. 
Herbivorous  animals,  213. 
Heredity,  and  evolution,  404 ; 

bearers  of,  251 ; 

definition,  249 ; 


426 


INDEX 


Heredity,  relation  of  alcohol  to,  372. 

Hervey,  William,  399. 

Hibernate,  22. 

Hides,  205. 

Hiluin,  59. 

Honey  and  wax,  207. 

Hookworm,  183,  228,  229. 

Horse,  ancestor  of,  193,  260. 

How  food  is  swallowed,  302. 

Human  blood,  314. 

Human  body,  a  machine,  267 ; 

composition  of,  21. 
Human  physiology,  definition,  15. 
Humming  bird,  43. 
Humus,  79. 

Hundred  calorie  portions,  286. 
Huxley,  398. 
Hybridizing,  254. 
Hybrids,  254. 
Hydra,  179. 
Hydrochloric  acid,  303. 
Hydrogen  of  water,  20,  20. 
Hydrophobia,  392. 
Hygiene,  27 ; 

of  breathing,  338 ; 

of  skin,  344 ; 

of  mouth,  302 ; 

of  muscles  and  bones,  268 ; 

outline,  415 ; 

personal,  261. 
Hypocotyl,  59. 
Hymenoptera,  30. 

Ichneumon  fly,  208. 
Illness  of  drinkers,  363. 
Imperfect  flowers,  44,  45. 
Immunity,  157,  390. 
Improvement,  by  selection,  253  ; 

of  man,  261. 
Impure  water,  289. 
Incisors,  301. 

Infectious  diseases,  27,  363,  390. 
Infusoria,  182. 
Inner  ear,  359. 
Inoculation,  157. 
Inorganic  soil,  77 ; 

foods,  274. 
Insects,  185; 

?^nd  foods,  370  J 


Insects,  as  disease  carriers,  225 ; 

as  pollinating  agents,  36  ; 

damage  done  by,  34,  214 ; 

diagram  of,  29 ; 

food  of,  33 ; 

of  the  house,  216 ; 

orders  of,  30. 
Inspection,  of  factories,  379 ; 

of  raw  food,  380. 
Instincts,  195. 
Internal  secretions,  317. 
Intestinal  fluid,  306 ; 

glands,  308. 
Intestine,  large,  309. 
Invertebrates,  185. 
Iris,  360. 
Isolation,  390. 

Jenner,  Edward,  400. 
Jimson  weed,  128. 
Jukes,  261. 

Kidney  bean,  59,  63. 
Kidneys,  181 ; 

human,  341 ; 

of  frog,  243. 
Kinetic  energy,  267. 
Knots,  112. 
Koch,  Robert,  403. 

Labor,  division  of,  178. 
Laboratory  equipment,  418. 
Lacteals,  309,  324. 
Lactic  acid,  150. 
Lactometer,  288. 
Ladybug,  209. 
Large  intestine,  309 ; 

of  frog,  243. 
Larva  of  milkweed  butterfly,  32. 
Latent  energy,  267. 
Lateral  line,  234. 
Leaves,  as  food,  117; 

evaporation  of  water  from,  85 ; 

cell  structure  of,  85 ; 

mosaic,  90 ; 

respiration,  96 ; 

section,  49 ; 

skeleton  of,  85 ; 

structure,  85,  86. 
Jjength  measures,  417, 


INDEX 


427 


Leopard  frog,  188. 
Lepidoptera,  30. 
Levers,  269. 

Life  comes  from  life,  399. 
Life  cycle,  104 ; 

of  plants,  103.     • 
Life  history  of  malarial  parasite,  217. 
Ligaments,  2G8. 
Ligature,  applying,  326. 
Light,  a  condition  of  environment, 
21,  22; 

and  bacteria,  145 ; 

effect  of,  22 ; 

necessary  for  starch  making,  91. 
Lighting  the  home,  376. 
Lily,  narrow  leaves,  90. 
Limewater  test,  64. 
Lister,  Sir  Joseph,  403. 
Liver,  306 ; 

a  storehouse,  307 ; 

effect  of  alcohol  on,  312 ; 

of  frog,  243. 
Living  matter  and  alcohol,  291 ; 

plant  and  animal  compared,  47 ; 

things,  needs  of,  266 ; 

things,  varying  sizes  of,  51. 
Lizard,  188. 
Lobster,  198. 
Locomotion,  181 ; 

of  frog,  241. 
Lowell,  typhoid  area,  384. 
Lumber  transporting,  110-111. 
Lungs,  air  passages,  330 ; 

changes  of  blood  in,  330. 
Lymph,  function,  317 ; 

glands  and  vessels,  324,  325. 
Lysol,  148. 

VEacNichol,  Dr.  T.  Alexander,  327. 

Macronucleus,  169. 

Malaria,  cause,  217. 

Malarial  mosquito,  218. 

Malarial  parasite,  life  history,  217. 

Mammal  development,  247 ; 

embryo,  247. 
Mammals,  191 ; 

adaptations,  192 ; 

as  food,  202 ; 

classification,  192. 


Mammary  glands,  191. 

Man,  animals  that  prey  upon,  230 ; 

and  his  environment,  266  ; 

circulation  of  blood,  318  ; 

improvement  of,  261 ; 

in  his  environment,  26 ; 

mouth  cavity,  300 ; 

place  in  nature,  195 ; 

races  of,  196 ; 

stomach,  303. 
Manufacture  of  fats,  93. 
Measures,  417. 

Mechanics  of  respiration,  332,  333. 
Membrane,  mucous,  299. 
Mendel,  Gregor,  257,  406. 
Mesenteric  glands,  309. 
Mesentery,  297. 
Mesoderm,  177. 

Metamorphosis  of  frog,  244,  245. 
Metchnikoff,  316. 
Methods,  of  cutting  timber.  111 ; 

of  breathing  in  vertebrates,  232. 
Micronucleus,  169. 
Micropyle,  59. 
Middle  ear,  359. 
Migration  of  fishes,  238. 
Milk,  and  tuberculosis,  381 ; 

composition  of,  273,  280 ; 

germs  in,  381 ; 

grades  of,  381 ; 

under  microscope,  150,  305. 
Milkweed,  butterfly,  32,  33. 
Milling  and  starch  making,  92. 
Mink,  205. 
Mixed  diet,  284. 
Moisture,  24,  78. 
Mollusca,  185. 
Mollusk,  185. 
Mold,  133,  134,  135 ; 

yeast  and  bacteria,  143. 
Morning  glory  embryo,  103. 
Mosquito,  malarial,  218; 

yelloAv  fever,  219. 
Moss  plant,  177. 
Mother  of  pearl,  206. 
Motor  nerves,  351. 
Mouth  cavity  in  man,  300,  300. 
Mouth  parts  of  bee,  38. 
Mucous  membrane,  299. 


428 


INDEX 


Mucus  cells,  299. 

Muscles  and  bones,  hygiene,  268. 

Mutations,  253,  406. 

Mutual    aid    between    flowers  and 

insects,  41. 
Mycelium,  133. 
Myriapoda,  185. 

Natural  environment,  25; 

selection,  253. 
Nectar,  35. 
Need,  of  food,  272 ; 

of  sleep,  356 ; 

of  ventilation,  335. 
Needs  of  living  things,  266. 
Nerve  cells  and  fatigue,  356 ; 

vasomotor,  325. 
Nervous  control,  181 ; 

of  heart,  325 ; 

of  respiration,  334 ; 

of  sweat  glands,  343. 
Nervous  system,  271,  349; 

of  frog,  352. 
Neuron,  diagram,  351. 
Newt,  187. 
Nicotine,  293. 

Nictitating  membrane  of  frog,  242. 
Nitrates,  80. 
Nitric  acid,  61. 
Nitrogen,  80; 

cycle,  162 ; 

fixing  bacteria,  80,  81,  151 ; 

of  air,  20. 
Nodules,  81. 

Normal  heat  output,  285. 
Nose  and  throat,  diseases,  340. 
Nucleus,  50. 
Nutrients,  273,  274 ; 

fuel  values,  277 ; 

in  common  foods,  275. 

Object  of  a  field  trip,  28. 
Oils,  test  for,  61. 
Operculum,  234. 
Ophidia,  189. 
Orbit  of  eye,  360. 
Orchard  fruits,  124. 
Organic  matter,  64. 
Organic  nutrients,  60. 


Organisms,  47. 
Organs,  47,  48,  180 ; 

of  Corti,  360 ; 

of  excretion,  340 ; 

of  hearing,  358 ; 

of  respiration,  -330 ; 

of  taste,  358 ; 

of  touch,  357. 
Orthoptera,  30. 
Osmosis,  definition,  75; 

experiment,  100 ; 

physiological  importance,  77. 
Ostrich,  191. 

Outline  of  courses,  407-414. 
Ovaries  of  frog,  243. 
Ovary,  36. 
Ovules,  54. 
Oxidation,  64; 

in  our  bodies,  65. 
Oxygen  cycle,  161 ; 

given  off  by  green  plants,  95 ; 

of  air,  20 ; 

of  water,  20. 
Oyster,  199,  200. 

Packard  (zoologist),  33. 
Palate,  hard  and  soft,  301. 
Palisade  tissue,  86. 
Pancreas,  305 ; 

of  frog,  243 ; 

work  of,  305. 
Papillae,  301. 
Pappus,  57. 
Paramoecium,  167,  168,  169; 

needs  of,  266 ; 

response  to  stimuli,  167. 
Parasites,  131. 

Parasitic  animals  cause  disease,  227. 
Parasitism,  cost  and  remedy,  263. 
Parotid,  299. 
Pasteur,  Louis,  401. 
Pasteurization,  146. 
Pea  pod,  55. 
Pearls,  206. 
Pectoral  fin,  233. 
Pelvic  fin,  233. 
Pepsin,  303. 
Peptic  gland,  304. 
Perfumes,  205. 


INDEX 


429 


Pericardium,  319. 

Peristaltic  waves,  303. 

Personal  hygiene,  261. 

Perspiration,  343. 

Petals,  35. 

Petri  dishes,  140. 

Phagocytes,  316. 

Pharynx,  301. 

Phenolphthalein,  80. 

Phosphoric  acid,  82. 

Photosynthesis,  92,  93. 

Physiology  of  mold,  133. 

Pistil,  36. 

Pith,  97. 

Placentae  of  mammal,  247. 

Plankton,  235. 

Plants,  animals  depend  on,  34 ; 

and  animals,  mutually  helpful,  18  ; 

classification,  176 ; 

food  for  insects,  33  ; 

as  food  makers,  88 ; 

function  of  parts,  48 ; 

groups,  174 ; 

need  minerals,  80 ; 

need  of  nitrogen,  80,  82 ; 

processes,  103; 

reproduction,  173. 
Plasma,  313. 

Plasmodium  malariae,  182,  217. 
Pleura,  332. 
Pleurococcus,  166. 
Plumule,  59. 
Pneumonia,  336. 
Pocket  garden,  73. 
Poison,  alcohol,  291 ; 

ivy,  128; 

produced  by  alcohol,  347. 
Polar  bear,  204. 
PoUen,  36 ; 

germination  of,  53,  54. 
PoUination,  36,  40 ; 

cross  and  self,  40 ; 

wind,  44. 
Pond  scum,  173. 
Pons,  352. 
Porifera,  182. 

Portal  cu-culation,  309,  322. 
Portions,  hundred  calorie,  286. 
Potato  beetle,  214. 


Potato  beetle,  embryo,  103. 
Premolars,  302. 
Preservatives,  147. 
Prevention  of  dyspepsia,  310 ; 

of  molds,  134. 
Proboscis,  30. 
Prologs,  32. 
Pronuba,  42,  43. 
Protecting  forests,  114. 
Proteins,  60,  273 ; 

making,  93 ; 

test  for,  61. 
Protoplasm,  50 ; 

what  it  can  do,  52. 
Protozoa,  172,  182,  205. 
Protozoan  diseases,  221. 
Pteridophytes,  176. 
Ptomaines,  144,  147. 
Ptyalin,  309. 
Public  hygiene,  389. 
Pulmonary  circulation,  320. 
Pulse,  cause,  323. 
Pupa  of  milkweed  butterfly,  33. 
Pupil  of  eye,  360. 
Pure  food  laws,  288. 
Purpose  of  digestion,  69,  296. 
Pyloric  casca,  235. 

Quarantine,  27,  390. 

Rabies,  392. 

Races  of  man,  196. 

Radiolaria,  182. 

Radiolarian  skeleton,  182. 

Recessive  characters,  258. 

Rectum,  297. 

Red  corpuscles,  313,  314. 

Reflex  actions,  353. 

Regulation  of  heat  of  body,  343. 

Relation,  of  age  to  diet,  280 ; 

of  alcohol  to  crime,  371 ; 

of  alcohol  to  heredity,  372  ; 

of  alcohol  to  pauperism,  371 ; 

of  animals  to  man,  17  ; 

of  bacteria  to  free  nitrogen,  81 ; 

of  bacteria  to  man,  16  ; 

of  biology  to  society,  18 ; 

of  cost  of  food  to  diet,  281 ; 

of  digestibility  to  diet,  281 ; 


430 


INDEX 


Relation,   of  environment    to    diet, 
280; 

of  green  plants  and  animals,  15, 
161,162; 

of  sex  to  diet,  280 ; 

of  work  to  diet,  277  ; 

of  yeasts  to  man,  135. 
Rennin,  303. 
Reproduction,  103,  181 ; 

importance  of,  52 ; 

in  seed  plants,  173,  174; 

of  cells,  50 ; 

of  Paramcecium,  169. 
Reptiles,  186. 
Reptilia,  188. 
Reserve  air,  334. 
Residual  air,  334. 
Respiration,  66,  181 ; 

and  alcohol,  346 ; 

and  nervous  control,  334 ; 

and  tobacco,  346 ; 

mechanics  of,  332,  333; 

necessity  for,  329 ; 

organs  of,  330 ; 

of  cells,  332 ; 

of  leaves,  96. 
Retina,  360. 
Rhizoids,  133. 
Rhizopoda,  182. 
Rice  field,  123. 
Ringworm,  134. 
Roaches,  216. 
Rock  fern,  175. 
Rockweed,  176. 
Roots  as  food,  119  ; 

as  food  storage,  83  ; 

downward  growth  of,  72  ; 

fine  structure,  73 ; 

give  out  acid,  79,  80 ; 

hairs,  74,  75 ; 

influence  of  gra\'ity,  72 ; 

influence  of  moisture,  73 ; 

passage  of  soil  water,  76  ; 

pressure,  101 ; 

system,   primary,  secondary,  ter- 
tiary roots,  72 ; 

uses  of,  71. 
Rotation  of  crops,  81. 
Roundworms,  183,  228. 


Rules  of  habit  formation,  356. 
Russian  thistle,  129. 

Saliva,  69,  299. 
Salivarj^  glands,  299 ; 

glands  of  frog,  243. 
Salmon,  201,  241. 
Sand  shark,  186. 
Sandworm,  184. 

Sanitarium  for  tuberculosis,  394. 
Sanitation,  27. 
Saprophytes,  131. 
Seavangers,  150. 
Schleiden  and  Schwann,  398. 
Schultz,  Max,  398. 
Sclerotic  coat,  360. 
Sea  anemones,  183. 
Secretion,  299,  306. 
Secretions,  internal,  317. 
Section,  of  ear,  359 ; 

of  timber,  111. 
Sedgwick,  William  T.,  312. 
Seed,  54 ; 

how  scattered,  56 ; 

plants,  reproduction,  174 ; 

why  it  grows,  58. 
Seedlings  of  bean,  63. 
Segmented  worms,  183. 
Selection,  artificial,  253 ; 

natural,  253. 
Selective  planting,  254. 
Semicircular  canal,  359. 
Sensations,  350. 
Sense  organs,  181 ; 

of  fish,  233 ; 

of  frog,  242. 
Senses,  357. 
Sensory  nerves,  351. 
Sepals,  35. 
Series,  animal,  182. 
Serum,  314. 
Sewage  disposal,  386. 
Sex,  relation  to  diet,  280. 
Shelf  fungi,  132. 
Sieve  tubes,  97. 

Simple  animal,  development,  177. 
Simplest  plants,  166. 
Skeleton,  of  dog,  185; 

of  fish,  237 ; 


INDEX 


431 


Skeleton,  of  leaf,  85; 

of  man,  268. 
Skin,  268 ; 

hygiene  of,  344. 
Skunk,  205. 
Sleep,  need  of,  356. 
Small  intestine,  307,  308. 
Smell,  sense  of,  358. 
Snail,  185. 
Snakes,  189 ; 

food  of,  212. 
Soft  palate,  301. 
Soil,  composition  of,  77 ; 

how  water  is  held  in,  77,  78. 
Sound,  character  of,  360. 
Sour  bread,  139. 
Soy  beans,  152. 
Sparrow,  246. 

Spawning  habits,  economic  impor- 
tance, 239. 
Species,  175,  194. 
Sperm,  177. 

Spermaries  of  frog,  243. 
Spermatophytes,  176. 
Spinal  cord  of  fish,  237. 
Spiracles,  29. 
Spirillum,  142. 
Sponge,  180,  182,  183,  206. 
Spore,  131,  173; 

plants,  174. 
Sporozoa,  182. 
Sprengel,  Conrad,  40. 
Squash  bug,  215. 
Stables,  clean  and  filthy,  388. 
Stamens,  36. 
Starch,  action  of  diastase,  60 ; 

digestion,  299 ; 

grains,  60 ; 

in  bean,  61 ; 

made  by  green  leaves,  90,  92 ; 

test  for,  61. 
Starch  making  and  milling,  92. 
Starfish,  184; 

food  of,  216. 
Stegomyia,  221. 
Stems,  as  food,  118; 

passage  of  fluids  up,  84 ; 

structure  of,  97. 
Sterilization,  145. 


Sterilizer,  140. 
Stigma,  36. 
Stimulants,  289. 
StuTup,  359. 
Stomata,  86,  88. 
Stomach,  297 ; 

digestive  experiments,  304 ; 

of  frog,  243 ; 

of  man,  303. 
Street  cleaning  department,  387. 
Structure,  colorless  corpuscles,  315  ; 

of  leaf,  85 ; 

of  red  corpuscle,  314 ; 

of  root,  73 ; 

of  root  hairs,  74. 
Sturgeon,  186. 
Style,  36. 

Sublingual  glands,  299. 
Submaxillary  glands,  299. 
Suffocation,  340. 
Sulphur,  149. 
Sun,  source  of  energy,  88. 
Sundew,  102. 
Sunlight  in  home,  374. 
Sweat  glands,  342. 
Sweeping  and  dusting,  336. 
Swim  bladder  of  fish,  236. 
Symbiosis,  163. 
Sympathetic  nerves,  352 ; 

nervous  system,  304,  350. 
Systematic  circulation,  320. 


Table     of     cost     of     food, 

283. 
Tactile  corpuscles,  357. 
Taenia  solium,  227. 
Tapeworm,  227. 
Taproot,  cross  section,  74. 
Taste  buds,  301,  358. 
Teeth,  301. 
Teleosts,  187. 
Temperature,  417 ; 

of  blood,  318. 
Tern,  190. 
Testa,  59. 
Test,  for  carbon  dioxide,  64: 

nutrients,  61,  68. 
Thallophytes,  176. 
Thoracic  duct,  324. 


276, 


432 


INDEX 


Tidal  air,  334. 

Timber,  methods  of  cutting.  111. 

Tissue  cells,  49,  179. 

Toad,  use  of,  209. 

Tobacco  and  oirculation,  328; 

and  respiration,  34(3 ; 

users  of,  293. 
Tortoise,  188. 
Touch,  357. 
Tourniquet,  326. 
Toxin,  152,  31(3. 
Trachea,  185. 
Transpiration,  85,  87. 
Transportation  of  lumber,  110,  111. 
Treatment     of    cuts     and    bruises, 

326. 
Trees,  need  of  city,  115; 

preventing  erosion,  108 ; 

regulate  water  supply,  105 ; 

value  of,  105. 
Trichina,  228. 
Trichinosis,  228. 
Trillium,  175. 
Trout,  development,  238. 
Trypanosomes,  221. 
Tuberculosis,  152,  153; 

and  milk,  381 ; 

how  to  fight,  393,  394. 
Tussock  moth,  215. 
T^vig,  section  of,  98. 
Tympanic  membrane,  358. 
Tympanum  of  frog,  242. 
Tyndall  box,  399. 
Typhoid,  224,  385 ; 

and  diarrhea,  200. 
Typhoid  fever,  152,  155,  382. 

Unit  characters,  258. 
Ureter,  342. 
Urethra,  342. 
Urine,  341. 
Urodela,  188. 
Uses,  of  animals,  198 ; 

of  antibodies,  316 ; 

of  green  plants,  1 17 ; 

of  ice,  377 ; 

of  nutrients,  274 ; 

of  protozoa,  172. 
Uterus  of  a  mammal,  247. 


Vaccination,  157,  221,  391. 
Vacuoles,  contracting,  168. 
Value,  of  insects,  208 ; 

of  trees,  105. 
Valves,  185,  319 ; 

in  vein,  324. 
Variation,  250. 
Vasomotor  nerves,  325. 
Vegetable  fibers  and  oils,  127. 
Veins,  318 ; 

function  and  structure,  323 ; 

valves,  324. 
Venae  cavae,  322. 
Ventilation,  335,  338. 
Ventricle,  319 ; 

of  fish  heart,  236. 
Venus  fly  trap,  102. 
Vermiform  appendix,  309. 
Vertebral  column,  186. 
Vertebrates,  breathing  of,  232. 
Villi,  308. 

Virginia  creeper,  128. 
Virus,  392. 
Vitreous  humor,  361. 
Vorticella,  171,  178. 
Vries,  Hugo  de,  253,  406. 

Warner,  Chas.  Dudley,  211. 
Waste  of  food,  287. 
Water,  275 ; 

composition  of,  20 ; 

impure,  289; 

supply,  383. 
Weed,  48,  128. 
Weights,  417. 
Wheat  crop,  121,  122. 
Wild  orchid,  40. 
Windpipe,  300,  301. 
Wood,  uses  of,  110. 
Work  of  cells,  270 ; 

of  Department  of  Agriculture,  255 

relation  to  diet,  277. 
Worms,  183. 

Yeasts,  136,  138,  139; 

relation  to  man,  135, 
Yellow  fever  mosquito,  219. 
Yucca,  42,  43. 

Zygospore,  174. 


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